Commit Graph

44733 Commits

Author SHA1 Message Date
Frederic Weisbecker
55911a9f42 rcu: Remove full memory barrier on RCU stall printout
RCU stall printout fetches the EQS state of a CPU with a preceding full
memory barrier. However there is nothing to order this read against at
this debugging stage. It is inherently racy when performed remotely.

Do a plain read instead.

This was the last user of rcu_dynticks_snap().

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
2024-06-28 06:44:12 -07:00
Frederic Weisbecker
e7a3c8ea6e rcu: Remove full memory barrier on boot time eqs sanity check
When the boot CPU initializes the per-CPU data on behalf of all possible
CPUs, a sanity check is performed on each of them to make sure none is
initialized in an extended quiescent state.

This check involves a full memory barrier which is useless at this early
boot stage.

Do a plain access instead.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
2024-06-28 06:44:12 -07:00
Frederic Weisbecker
33c0860bf7 rcu/exp: Remove superfluous full memory barrier upon first EQS snapshot
When the grace period kthread checks the extended quiescent state
counter of a CPU, full ordering is necessary to ensure that either:

* If the GP kthread observes the remote target in an extended quiescent
  state, then that target must observe all accesses prior to the current
  grace period, including the current grace period sequence number, once
  it exits that extended quiescent state.

or:

* If the GP kthread observes the remote target NOT in an extended
  quiescent state, then the target further entering in an extended
  quiescent state must observe all accesses prior to the current
  grace period, including the current grace period sequence number, once
  it enters that extended quiescent state.

This ordering is enforced through a full memory barrier placed right
before taking the first EQS snapshot. However this is superfluous
because the snapshot is taken while holding the target's rnp lock which
provides the necessary ordering through its chain of
smp_mb__after_unlock_lock().

Remove the needless explicit barrier before the snapshot and put a
comment about the implicit barrier newly relied upon here.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2024-06-28 06:43:34 -07:00
Frederic Weisbecker
9a7e73c9be rcu: Remove superfluous full memory barrier upon first EQS snapshot
When the grace period kthread checks the extended quiescent state
counter of a CPU, full ordering is necessary to ensure that either:

* If the GP kthread observes the remote target in an extended quiescent
  state, then that target must observe all accesses prior to the current
  grace period, including the current grace period sequence number, once
  it exits that extended quiescent state.

or:

* If the GP kthread observes the remote target NOT in an extended
  quiescent state, then the target further entering in an extended
  quiescent state must observe all accesses prior to the current
  grace period, including the current grace period sequence number, once
  it enters that extended quiescent state.

This ordering is enforced through a full memory barrier placed right
before taking the first EQS snapshot. However this is superfluous
because the snapshot is taken while holding the target's rnp lock which
provides the necessary ordering through its chain of
smp_mb__after_unlock_lock().

Remove the needless explicit barrier before the snapshot and put a
comment about the implicit barrier newly relied upon here.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2024-06-28 06:43:34 -07:00
Frederic Weisbecker
0a5e9bd31e rcu: Remove full ordering on second EQS snapshot
When the grace period kthread checks the extended quiescent state
counter of a CPU, full ordering is necessary to ensure that either:

* If the GP kthread observes the remote target in an extended quiescent
  state, then that target must observe all accesses prior to the current
  grace period, including the current grace period sequence number, once
  it exits that extended quiescent state. Also the GP kthread must
  observe all accesses performed by the target prior it entering in
  EQS.

or:

* If the GP kthread observes the remote target NOT in an extended
  quiescent state, then the target further entering in an extended
  quiescent state must observe all accesses prior to the current
  grace period, including the current grace period sequence number, once
  it enters that extended quiescent state. Also the GP kthread later
  observing that EQS must also observe all accesses performed by the
  target prior it entering in EQS.

This ordering is explicitly performed both on the first EQS snapshot
and on the second one as well through the combination of a preceding
full barrier followed by an acquire read. However the second snapshot's
full memory barrier is redundant and not needed to enforce the above
guarantees:

    GP kthread                  Remote target
    ----                        -----
    // Access prior GP
    WRITE_ONCE(A, 1)
    // first snapshot
    smp_mb()
    x = smp_load_acquire(EQS)
                               // Access prior GP
                               WRITE_ONCE(B, 1)
                               // EQS enter
                               // implied full barrier by atomic_add_return()
                               atomic_add_return(RCU_DYNTICKS_IDX, EQS)
                               // implied full barrier by atomic_add_return()
                               READ_ONCE(A)
    // second snapshot
    y = smp_load_acquire(EQS)
    z = READ_ONCE(B)

If the GP kthread above fails to observe the remote target in EQS
(x not in EQS), the remote target will observe A == 1 after further
entering in EQS. Then the second snapshot taken by the GP kthread only
need to be an acquire read in order to observe z == 1.

Therefore remove the needless full memory barrier on second snapshot.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2024-06-28 06:43:33 -07:00
Linus Torvalds
a0db36ed57 Merge tag 'irq-urgent-2024-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull irq fixes from Ingo Molnar:

 - Fix x86 IRQ vector leak caused by a CPU offlining race

 - Fix build failure in the riscv-imsic irqchip driver
   caused by an API-change semantic conflict

 - Fix use-after-free in irq_find_at_or_after()

* tag 'irq-urgent-2024-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  genirq/irqdesc: Prevent use-after-free in irq_find_at_or_after()
  genirq/cpuhotplug, x86/vector: Prevent vector leak during CPU offline
  irqchip/riscv-imsic: Fixup riscv_ipi_set_virq_range() conflict
2024-05-25 14:48:40 -07:00
Linus Torvalds
0b32d436c0 Merge tag 'mm-stable-2024-05-24-11-49' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull more mm updates from Andrew Morton:
 "Jeff Xu's implementation of the mseal() syscall"

* tag 'mm-stable-2024-05-24-11-49' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
  selftest mm/mseal read-only elf memory segment
  mseal: add documentation
  selftest mm/mseal memory sealing
  mseal: add mseal syscall
  mseal: wire up mseal syscall
2024-05-24 12:47:28 -07:00
dicken.ding
b84a8aba80 genirq/irqdesc: Prevent use-after-free in irq_find_at_or_after()
irq_find_at_or_after() dereferences the interrupt descriptor which is
returned by mt_find() while neither holding sparse_irq_lock nor RCU read
lock, which means the descriptor can be freed between mt_find() and the
dereference:

    CPU0                            CPU1
    desc = mt_find()
                                    delayed_free_desc(desc)
    irq_desc_get_irq(desc)

The use-after-free is reported by KASAN:

    Call trace:
     irq_get_next_irq+0x58/0x84
     show_stat+0x638/0x824
     seq_read_iter+0x158/0x4ec
     proc_reg_read_iter+0x94/0x12c
     vfs_read+0x1e0/0x2c8

    Freed by task 4471:
     slab_free_freelist_hook+0x174/0x1e0
     __kmem_cache_free+0xa4/0x1dc
     kfree+0x64/0x128
     irq_kobj_release+0x28/0x3c
     kobject_put+0xcc/0x1e0
     delayed_free_desc+0x14/0x2c
     rcu_do_batch+0x214/0x720

Guard the access with a RCU read lock section.

Fixes: 721255b982 ("genirq: Use a maple tree for interrupt descriptor management")
Signed-off-by: dicken.ding <dicken.ding@mediatek.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240524091739.31611-1-dicken.ding@mediatek.com
2024-05-24 12:49:35 +02:00
Jeff Xu
ff388fe5c4 mseal: wire up mseal syscall
Patch series "Introduce mseal", v10.

This patchset proposes a new mseal() syscall for the Linux kernel.

In a nutshell, mseal() protects the VMAs of a given virtual memory range
against modifications, such as changes to their permission bits.

Modern CPUs support memory permissions, such as the read/write (RW) and
no-execute (NX) bits.  Linux has supported NX since the release of kernel
version 2.6.8 in August 2004 [1].  The memory permission feature improves
the security stance on memory corruption bugs, as an attacker cannot
simply write to arbitrary memory and point the code to it.  The memory
must be marked with the X bit, or else an exception will occur. 
Internally, the kernel maintains the memory permissions in a data
structure called VMA (vm_area_struct).  mseal() additionally protects the
VMA itself against modifications of the selected seal type.

Memory sealing is useful to mitigate memory corruption issues where a
corrupted pointer is passed to a memory management system.  For example,
such an attacker primitive can break control-flow integrity guarantees
since read-only memory that is supposed to be trusted can become writable
or .text pages can get remapped.  Memory sealing can automatically be
applied by the runtime loader to seal .text and .rodata pages and
applications can additionally seal security critical data at runtime.  A
similar feature already exists in the XNU kernel with the
VM_FLAGS_PERMANENT [3] flag and on OpenBSD with the mimmutable syscall
[4].  Also, Chrome wants to adopt this feature for their CFI work [2] and
this patchset has been designed to be compatible with the Chrome use case.

Two system calls are involved in sealing the map:  mmap() and mseal().

The new mseal() is an syscall on 64 bit CPU, and with following signature:

int mseal(void addr, size_t len, unsigned long flags)
addr/len: memory range.
flags: reserved.

mseal() blocks following operations for the given memory range.

1> Unmapping, moving to another location, and shrinking the size,
   via munmap() and mremap(), can leave an empty space, therefore can
   be replaced with a VMA with a new set of attributes.

2> Moving or expanding a different VMA into the current location,
   via mremap().

3> Modifying a VMA via mmap(MAP_FIXED).

4> Size expansion, via mremap(), does not appear to pose any specific
   risks to sealed VMAs. It is included anyway because the use case is
   unclear. In any case, users can rely on merging to expand a sealed VMA.

5> mprotect() and pkey_mprotect().

6> Some destructive madvice() behaviors (e.g. MADV_DONTNEED) for anonymous
   memory, when users don't have write permission to the memory. Those
   behaviors can alter region contents by discarding pages, effectively a
   memset(0) for anonymous memory.

The idea that inspired this patch comes from Stephen Röttger’s work in
V8 CFI [5].  Chrome browser in ChromeOS will be the first user of this
API.

Indeed, the Chrome browser has very specific requirements for sealing,
which are distinct from those of most applications.  For example, in the
case of libc, sealing is only applied to read-only (RO) or read-execute
(RX) memory segments (such as .text and .RELRO) to prevent them from
becoming writable, the lifetime of those mappings are tied to the lifetime
of the process.

Chrome wants to seal two large address space reservations that are managed
by different allocators.  The memory is mapped RW- and RWX respectively
but write access to it is restricted using pkeys (or in the future ARM
permission overlay extensions).  The lifetime of those mappings are not
tied to the lifetime of the process, therefore, while the memory is
sealed, the allocators still need to free or discard the unused memory. 
For example, with madvise(DONTNEED).

However, always allowing madvise(DONTNEED) on this range poses a security
risk.  For example if a jump instruction crosses a page boundary and the
second page gets discarded, it will overwrite the target bytes with zeros
and change the control flow.  Checking write-permission before the discard
operation allows us to control when the operation is valid.  In this case,
the madvise will only succeed if the executing thread has PKEY write
permissions and PKRU changes are protected in software by control-flow
integrity.

Although the initial version of this patch series is targeting the Chrome
browser as its first user, it became evident during upstream discussions
that we would also want to ensure that the patch set eventually is a
complete solution for memory sealing and compatible with other use cases. 
The specific scenario currently in mind is glibc's use case of loading and
sealing ELF executables.  To this end, Stephen is working on a change to
glibc to add sealing support to the dynamic linker, which will seal all
non-writable segments at startup.  Once this work is completed, all
applications will be able to automatically benefit from these new
protections.

In closing, I would like to formally acknowledge the valuable
contributions received during the RFC process, which were instrumental in
shaping this patch:

Jann Horn: raising awareness and providing valuable insights on the
  destructive madvise operations.
Liam R. Howlett: perf optimization.
Linus Torvalds: assisting in defining system call signature and scope.
Theo de Raadt: sharing the experiences and insight gained from
  implementing mimmutable() in OpenBSD.

MM perf benchmarks
==================
This patch adds a loop in the mprotect/munmap/madvise(DONTNEED) to
check the VMAs’ sealing flag, so that no partial update can be made,
when any segment within the given memory range is sealed.

To measure the performance impact of this loop, two tests are developed.
[8]

The first is measuring the time taken for a particular system call,
by using clock_gettime(CLOCK_MONOTONIC). The second is using
PERF_COUNT_HW_REF_CPU_CYCLES (exclude user space). Both tests have
similar results.

The tests have roughly below sequence:
for (i = 0; i < 1000, i++)
    create 1000 mappings (1 page per VMA)
    start the sampling
    for (j = 0; j < 1000, j++)
        mprotect one mapping
    stop and save the sample
    delete 1000 mappings
calculates all samples.

Below tests are performed on Intel(R) Pentium(R) Gold 7505 @ 2.00GHz,
4G memory, Chromebook.

Based on the latest upstream code:
The first test (measuring time)
syscall__	vmas	t	t_mseal	delta_ns	per_vma	%
munmap__  	1	909	944	35	35	104%
munmap__  	2	1398	1502	104	52	107%
munmap__  	4	2444	2594	149	37	106%
munmap__  	8	4029	4323	293	37	107%
munmap__  	16	6647	6935	288	18	104%
munmap__  	32	11811	12398	587	18	105%
mprotect	1	439	465	26	26	106%
mprotect	2	1659	1745	86	43	105%
mprotect	4	3747	3889	142	36	104%
mprotect	8	6755	6969	215	27	103%
mprotect	16	13748	14144	396	25	103%
mprotect	32	27827	28969	1142	36	104%
madvise_	1	240	262	22	22	109%
madvise_	2	366	442	76	38	121%
madvise_	4	623	751	128	32	121%
madvise_	8	1110	1324	215	27	119%
madvise_	16	2127	2451	324	20	115%
madvise_	32	4109	4642	534	17	113%

The second test (measuring cpu cycle)
syscall__	vmas	cpu	cmseal	delta_cpu	per_vma	%
munmap__	1	1790	1890	100	100	106%
munmap__	2	2819	3033	214	107	108%
munmap__	4	4959	5271	312	78	106%
munmap__	8	8262	8745	483	60	106%
munmap__	16	13099	14116	1017	64	108%
munmap__	32	23221	24785	1565	49	107%
mprotect	1	906	967	62	62	107%
mprotect	2	3019	3203	184	92	106%
mprotect	4	6149	6569	420	105	107%
mprotect	8	9978	10524	545	68	105%
mprotect	16	20448	21427	979	61	105%
mprotect	32	40972	42935	1963	61	105%
madvise_	1	434	497	63	63	115%
madvise_	2	752	899	147	74	120%
madvise_	4	1313	1513	200	50	115%
madvise_	8	2271	2627	356	44	116%
madvise_	16	4312	4883	571	36	113%
madvise_	32	8376	9319	943	29	111%

Based on the result, for 6.8 kernel, sealing check adds
20-40 nano seconds, or around 50-100 CPU cycles, per VMA.

In addition, I applied the sealing to 5.10 kernel:
The first test (measuring time)
syscall__	vmas	t	tmseal	delta_ns	per_vma	%
munmap__	1	357	390	33	33	109%
munmap__	2	442	463	21	11	105%
munmap__	4	614	634	20	5	103%
munmap__	8	1017	1137	120	15	112%
munmap__	16	1889	2153	263	16	114%
munmap__	32	4109	4088	-21	-1	99%
mprotect	1	235	227	-7	-7	97%
mprotect	2	495	464	-30	-15	94%
mprotect	4	741	764	24	6	103%
mprotect	8	1434	1437	2	0	100%
mprotect	16	2958	2991	33	2	101%
mprotect	32	6431	6608	177	6	103%
madvise_	1	191	208	16	16	109%
madvise_	2	300	324	24	12	108%
madvise_	4	450	473	23	6	105%
madvise_	8	753	806	53	7	107%
madvise_	16	1467	1592	125	8	108%
madvise_	32	2795	3405	610	19	122%
					
The second test (measuring cpu cycle)
syscall__	nbr_vma	cpu	cmseal	delta_cpu	per_vma	%
munmap__	1	684	715	31	31	105%
munmap__	2	861	898	38	19	104%
munmap__	4	1183	1235	51	13	104%
munmap__	8	1999	2045	46	6	102%
munmap__	16	3839	3816	-23	-1	99%
munmap__	32	7672	7887	216	7	103%
mprotect	1	397	443	46	46	112%
mprotect	2	738	788	50	25	107%
mprotect	4	1221	1256	35	9	103%
mprotect	8	2356	2429	72	9	103%
mprotect	16	4961	4935	-26	-2	99%
mprotect	32	9882	10172	291	9	103%
madvise_	1	351	380	29	29	108%
madvise_	2	565	615	49	25	109%
madvise_	4	872	933	61	15	107%
madvise_	8	1508	1640	132	16	109%
madvise_	16	3078	3323	245	15	108%
madvise_	32	5893	6704	811	25	114%

For 5.10 kernel, sealing check adds 0-15 ns in time, or 10-30
CPU cycles, there is even decrease in some cases.

It might be interesting to compare 5.10 and 6.8 kernel
The first test (measuring time)
syscall__	vmas	t_5_10	t_6_8	delta_ns	per_vma	%
munmap__	1	357	909	552	552	254%
munmap__	2	442	1398	956	478	316%
munmap__	4	614	2444	1830	458	398%
munmap__	8	1017	4029	3012	377	396%
munmap__	16	1889	6647	4758	297	352%
munmap__	32	4109	11811	7702	241	287%
mprotect	1	235	439	204	204	187%
mprotect	2	495	1659	1164	582	335%
mprotect	4	741	3747	3006	752	506%
mprotect	8	1434	6755	5320	665	471%
mprotect	16	2958	13748	10790	674	465%
mprotect	32	6431	27827	21397	669	433%
madvise_	1	191	240	49	49	125%
madvise_	2	300	366	67	33	122%
madvise_	4	450	623	173	43	138%
madvise_	8	753	1110	357	45	147%
madvise_	16	1467	2127	660	41	145%
madvise_	32	2795	4109	1314	41	147%

The second test (measuring cpu cycle)
syscall__	vmas	cpu_5_10	c_6_8	delta_cpu	per_vma	%
munmap__	1	684	1790	1106	1106	262%
munmap__	2	861	2819	1958	979	327%
munmap__	4	1183	4959	3776	944	419%
munmap__	8	1999	8262	6263	783	413%
munmap__	16	3839	13099	9260	579	341%
munmap__	32	7672	23221	15549	486	303%
mprotect	1	397	906	509	509	228%
mprotect	2	738	3019	2281	1140	409%
mprotect	4	1221	6149	4929	1232	504%
mprotect	8	2356	9978	7622	953	423%
mprotect	16	4961	20448	15487	968	412%
mprotect	32	9882	40972	31091	972	415%
madvise_	1	351	434	82	82	123%
madvise_	2	565	752	186	93	133%
madvise_	4	872	1313	442	110	151%
madvise_	8	1508	2271	763	95	151%
madvise_	16	3078	4312	1234	77	140%
madvise_	32	5893	8376	2483	78	142%

From 5.10 to 6.8
munmap: added 250-550 ns in time, or 500-1100 in cpu cycle, per vma.
mprotect: added 200-750 ns in time, or 500-1200 in cpu cycle, per vma.
madvise: added 33-50 ns in time, or 70-110 in cpu cycle, per vma.

In comparison to mseal, which adds 20-40 ns or 50-100 CPU cycles, the
increase from 5.10 to 6.8 is significantly larger, approximately ten times
greater for munmap and mprotect.

When I discuss the mm performance with Brian Makin, an engineer who worked
on performance, it was brought to my attention that such performance
benchmarks, which measuring millions of mm syscall in a tight loop, may
not accurately reflect real-world scenarios, such as that of a database
service.  Also this is tested using a single HW and ChromeOS, the data
from another HW or distribution might be different.  It might be best to
take this data with a grain of salt.


This patch (of 5):

Wire up mseal syscall for all architectures.

Link: https://lkml.kernel.org/r/20240415163527.626541-1-jeffxu@chromium.org
Link: https://lkml.kernel.org/r/20240415163527.626541-2-jeffxu@chromium.org
Signed-off-by: Jeff Xu <jeffxu@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Jann Horn <jannh@google.com> [Bug #2]
Cc: Jeff Xu <jeffxu@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jorge Lucangeli Obes <jorgelo@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Pedro Falcato <pedro.falcato@gmail.com>
Cc: Stephen Röttger <sroettger@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Amer Al Shanawany <amer.shanawany@gmail.com>
Cc: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-05-23 19:40:26 -07:00
Dongli Zhang
a6c11c0a52 genirq/cpuhotplug, x86/vector: Prevent vector leak during CPU offline
The absence of IRQD_MOVE_PCNTXT prevents immediate effectiveness of
interrupt affinity reconfiguration via procfs. Instead, the change is
deferred until the next instance of the interrupt being triggered on the
original CPU.

When the interrupt next triggers on the original CPU, the new affinity is
enforced within __irq_move_irq(). A vector is allocated from the new CPU,
but the old vector on the original CPU remains and is not immediately
reclaimed. Instead, apicd->move_in_progress is flagged, and the reclaiming
process is delayed until the next trigger of the interrupt on the new CPU.

Upon the subsequent triggering of the interrupt on the new CPU,
irq_complete_move() adds a task to the old CPU's vector_cleanup list if it
remains online. Subsequently, the timer on the old CPU iterates over its
vector_cleanup list, reclaiming old vectors.

However, a rare scenario arises if the old CPU is outgoing before the
interrupt triggers again on the new CPU.

In that case irq_force_complete_move() is not invoked on the outgoing CPU
to reclaim the old apicd->prev_vector because the interrupt isn't currently
affine to the outgoing CPU, and irq_needs_fixup() returns false. Even
though __vector_schedule_cleanup() is later called on the new CPU, it
doesn't reclaim apicd->prev_vector; instead, it simply resets both
apicd->move_in_progress and apicd->prev_vector to 0.

As a result, the vector remains unreclaimed in vector_matrix, leading to a
CPU vector leak.

To address this issue, move the invocation of irq_force_complete_move()
before the irq_needs_fixup() call to reclaim apicd->prev_vector, if the
interrupt is currently or used to be affine to the outgoing CPU.

Additionally, reclaim the vector in __vector_schedule_cleanup() as well,
following a warning message, although theoretically it should never see
apicd->move_in_progress with apicd->prev_cpu pointing to an offline CPU.

Fixes: f0383c24b4 ("genirq/cpuhotplug: Add support for cleaning up move in progress")
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240522220218.162423-1-dongli.zhang@oracle.com
2024-05-23 21:51:50 +02:00
Linus Torvalds
404001ddf3 Merge tag 'trace-fixes-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing fixes from Steven Rostedt:
 "Minor last minute fixes:

   - Fix a very tight race between the ring buffer readers and resizing
     the ring buffer

   - Correct some stale comments in the ring buffer code

   - Fix kernel-doc in the rv code

   - Add a MODULE_DESCRIPTION to preemptirq_delay_test"

* tag 'trace-fixes-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  rv: Update rv_en(dis)able_monitor doc to match kernel-doc
  tracing: Add MODULE_DESCRIPTION() to preemptirq_delay_test
  ring-buffer: Fix a race between readers and resize checks
  ring-buffer: Correct stale comments related to non-consuming readers
2024-05-23 12:36:38 -07:00
Linus Torvalds
d6a326d694 Merge tag 'trace-assign-str-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing cleanup from Steven Rostedt:
 "Remove second argument of __assign_str()

  The __assign_str() macro logic of the TRACE_EVENT() macro was
  optimized so that it no longer needs the second argument. The
  __assign_str() is always matched with __string() field that takes a
  field name and the source for that field:

    __string(field, source)

  The TRACE_EVENT() macro logic will save off the source value and then
  use that value to copy into the ring buffer via the __assign_str().

  Before commit c1fa617cae ("tracing: Rework __assign_str() and
  __string() to not duplicate getting the string"), the __assign_str()
  needed the second argument which would perform the same logic as the
  __string() source parameter did. Not only would this add overhead, but
  it was error prone as if the __assign_str() source produced something
  different, it may not have allocated enough for the string in the ring
  buffer (as the __string() source was used to determine how much to
  allocate)

  Now that the __assign_str() just uses the same string that was used in
  __string() it no longer needs the source parameter. It can now be
  removed"

* tag 'trace-assign-str-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing/treewide: Remove second parameter of __assign_str()
2024-05-23 12:28:01 -07:00
Linus Torvalds
2ef32ad224 Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost
Pull virtio updates from Michael Tsirkin:
 "Several new features here:

   - virtio-net is finally supported in vduse

   - virtio (balloon and mem) interaction with suspend is improved

   - vhost-scsi now handles signals better/faster

  And fixes, cleanups all over the place"

* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost: (48 commits)
  virtio-pci: Check if is_avq is NULL
  virtio: delete vq in vp_find_vqs_msix() when request_irq() fails
  MAINTAINERS: add Eugenio Pérez as reviewer
  vhost-vdpa: Remove usage of the deprecated ida_simple_xx() API
  vp_vdpa: don't allocate unused msix vectors
  sound: virtio: drop owner assignment
  fuse: virtio: drop owner assignment
  scsi: virtio: drop owner assignment
  rpmsg: virtio: drop owner assignment
  nvdimm: virtio_pmem: drop owner assignment
  wifi: mac80211_hwsim: drop owner assignment
  vsock/virtio: drop owner assignment
  net: 9p: virtio: drop owner assignment
  net: virtio: drop owner assignment
  net: caif: virtio: drop owner assignment
  misc: nsm: drop owner assignment
  iommu: virtio: drop owner assignment
  drm/virtio: drop owner assignment
  gpio: virtio: drop owner assignment
  firmware: arm_scmi: virtio: drop owner assignment
  ...
2024-05-23 12:04:36 -07:00
Steven Rostedt (Google)
2c92ca849f tracing/treewide: Remove second parameter of __assign_str()
With the rework of how the __string() handles dynamic strings where it
saves off the source string in field in the helper structure[1], the
assignment of that value to the trace event field is stored in the helper
value and does not need to be passed in again.

This means that with:

  __string(field, mystring)

Which use to be assigned with __assign_str(field, mystring), no longer
needs the second parameter and it is unused. With this, __assign_str()
will now only get a single parameter.

There's over 700 users of __assign_str() and because coccinelle does not
handle the TRACE_EVENT() macro I ended up using the following sed script:

  git grep -l __assign_str | while read a ; do
      sed -e 's/\(__assign_str([^,]*[^ ,]\) *,[^;]*/\1)/' $a > /tmp/test-file;
      mv /tmp/test-file $a;
  done

I then searched for __assign_str() that did not end with ';' as those
were multi line assignments that the sed script above would fail to catch.

Note, the same updates will need to be done for:

  __assign_str_len()
  __assign_rel_str()
  __assign_rel_str_len()

I tested this with both an allmodconfig and an allyesconfig (build only for both).

[1] https://lore.kernel.org/linux-trace-kernel/20240222211442.634192653@goodmis.org/

Link: https://lore.kernel.org/linux-trace-kernel/20240516133454.681ba6a0@rorschach.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Christian König <christian.koenig@amd.com> for the amdgpu parts.
Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> #for
Acked-by: Rafael J. Wysocki <rafael@kernel.org> # for thermal
Acked-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Darrick J. Wong <djwong@kernel.org>	# xfs
Tested-by: Guenter Roeck <linux@roeck-us.net>
2024-05-22 20:14:47 -04:00
Linus Torvalds
d90be6e4aa Merge tag 'driver-core-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core
Pull driver core updates from Greg KH:
 "Here is the small set of driver core and kernfs changes for 6.10-rc1.

  Nothing major here at all, just a small set of changes for some driver
  core apis, and minor fixups. Included in here are:

   - sysfs_bin_attr_simple_read() helper added and used

   - device_show_string() helper added and used

  All usages of these were acked by the various maintainers. Also in
  here are:

   - kernfs minor cleanup

   - removed unused functions

   - typo fix in documentation

   - pay attention to sysfs_create_link() failures in module.c finally

  All of these have been in linux-next for a very long time with no
  reported problems"

* tag 'driver-core-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  device property: Fix a typo in the description of device_get_child_node_count()
  kernfs: mount: Remove unnecessary ‘NULL’ values from knparent
  scsi: Use device_show_string() helper for sysfs attributes
  platform/x86: Use device_show_string() helper for sysfs attributes
  perf: Use device_show_string() helper for sysfs attributes
  IB/qib: Use device_show_string() helper for sysfs attributes
  hwmon: Use device_show_string() helper for sysfs attributes
  driver core: Add device_show_string() helper for sysfs attributes
  treewide: Use sysfs_bin_attr_simple_read() helper
  sysfs: Add sysfs_bin_attr_simple_read() helper
  module: don't ignore sysfs_create_link() failures
  driver core: Remove unused platform_notify, platform_notify_remove
2024-05-22 12:13:40 -07:00
Linus Torvalds
f6b8e86b7a Merge tag 'tty-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty
Pull tty / serial updates from Greg KH:
 "Here is the big set of tty/serial driver changes for 6.10-rc1.
  Included in here are:

   - Usual good set of api cleanups and evolution by Jiri Slaby to make
     the serial interfaces move out of the 1990's by using kfifos
     instead of hand-rolling their own logic.

   - 8250_exar driver updates

   - max3100 driver updates

   - sc16is7xx driver updates

   - exar driver updates

   - sh-sci driver updates

   - tty ldisc api addition to help refuse bindings

   - other smaller serial driver updates

  All of these have been in linux-next for a while with no reported
  issues"

* tag 'tty-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (113 commits)
  serial: Clear UPF_DEAD before calling tty_port_register_device_attr_serdev()
  serial: imx: Raise TX trigger level to 8
  serial: 8250_pnp: Simplify "line" related code
  serial: sh-sci: simplify locking when re-issuing RXDMA fails
  serial: sh-sci: let timeout timer only run when DMA is scheduled
  serial: sh-sci: describe locking requirements for invalidating RXDMA
  serial: sh-sci: protect invalidating RXDMA on shutdown
  tty: add the option to have a tty reject a new ldisc
  serial: core: Call device_set_awake_path() for console port
  dt-bindings: serial: brcm,bcm2835-aux-uart: convert to dtschema
  tty: serial: uartps: Add support for uartps controller reset
  arm64: zynqmp: Add resets property for UART nodes
  dt-bindings: serial: cdns,uart: Add optional reset property
  serial: 8250_pnp: Switch to DEFINE_SIMPLE_DEV_PM_OPS()
  serial: 8250_exar: Keep the includes sorted
  serial: 8250_exar: Make type of bit the same in exar_ee_*_bit()
  serial: 8250_exar: Use BIT() in exar_ee_read()
  serial: 8250_exar: Switch to use dev_err_probe()
  serial: 8250_exar: Return directly from switch-cases
  serial: 8250_exar: Decrease indentation level
  ...
2024-05-22 11:53:02 -07:00
Linus Torvalds
f3033eb791 Merge tag 'leds-next-6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/leds
Pull LED updates from Lee Jones:
 "Core Frameworks:
   - Ensure seldom updated triggers have a brightness value before first
     update

  New Device Support:
   - Add support for Simatic IPC Device BX_59A to IPC LEDs Core
   - Add support for Qualcomm PMI8950 PWM to LPG Core

  New Functionality:
   - Add a bunch of new LED function identifiers
   - Add support for High Resolution Timers in LED Trigger Patten

  Fix-ups:
   - Shift out Audio Trigger to the Sound subsystem
   - Convert suitable calls to devm_* managed resources
   - Device Tree binding adaptions/conversions/creation
   - Remove superfluous code/variables/attributes and simplify overall
   - Use/convert to new/better APIs/helpers/MACROs instead of
     hand-rolling implementations

  Bug Fixes:
   - Repair enabling Torch Mode from V4L2 on the second LED
   - Ensure PWM is disabled when suspending"

* tag 'leds-next-6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/leds: (28 commits)
  leds: mt6370: Remove unused field 'reg_cfgs' from 'struct mt6370_priv'
  leds: lp50xx: Remove unused field 'num_of_banked_leds' from 'struct lp50xx'
  leds: lp50xx: Remove unused field 'bank_modules' from 'struct lp50xx_led'
  leds: aat1290: Remove unused field 'torch_brightness' from 'struct aat1290_led'
  leds: sun50i-a100: Use match_string() helper to simplify the code
  leds: pwm: Disable PWM when going to suspend
  leds: trigger: pattern: Add support for hrtimer
  leds: mt6360: Fix the second LED can not enable torch mode by V4L2
  dt-bindings: leds: leds-qcom-lpg: Add support for PMI8950 PWM
  leds: qcom-lpg: Add support for PMI8950 PWM
  leds: apu: Remove duplicate DMI lookup data
  leds: trigger: netdev: Remove not needed call to led_set_brightness in deactivate
  dt-bindings: leds: Add LED_FUNCTION_SPEED_* for link speed on LAN/WAN
  dt-bindings: leds: Add LED_FUNCTION_MOBILE for mobile network
  leds: simatic-ipc-leds-gpio: Add support for module BX-59A
  dt-bindings: leds: qcom-lpg: Document PM6150L compatible
  dt-bindings: leds: pca963x: Convert text bindings to YAML
  leds: an30259a: Use devm_mutex_init() for mutex initialization
  leds: mlxreg: Use devm_mutex_init() for mutex initialization
  leds: nic78bx: Use devm API to cleanup module's resources
  ...
2024-05-22 10:49:54 -07:00
Linus Torvalds
0bfbc914d9 Merge tag 'riscv-for-linus-6.10-mw1' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux
Pull RISC-V updates from Palmer Dabbelt:

 - Add byte/half-word compare-and-exchange, emulated via LR/SC loops

 - Support for Rust

 - Support for Zihintpause in hwprobe

 - Add PR_RISCV_SET_ICACHE_FLUSH_CTX prctl()

 - Support lockless lockrefs

* tag 'riscv-for-linus-6.10-mw1' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux: (42 commits)
  riscv: defconfig: Enable CONFIG_CLK_SOPHGO_CV1800
  riscv: select ARCH_HAS_FAST_MULTIPLIER
  riscv: mm: still create swiotlb buffer for kmalloc() bouncing if required
  riscv: Annotate pgtable_l{4,5}_enabled with __ro_after_init
  riscv: Remove redundant CONFIG_64BIT from pgtable_l{4,5}_enabled
  riscv: mm: Always use an ASID to flush mm contexts
  riscv: mm: Preserve global TLB entries when switching contexts
  riscv: mm: Make asid_bits a local variable
  riscv: mm: Use a fixed layout for the MM context ID
  riscv: mm: Introduce cntx2asid/cntx2version helper macros
  riscv: Avoid TLB flush loops when affected by SiFive CIP-1200
  riscv: Apply SiFive CIP-1200 workaround to single-ASID sfence.vma
  riscv: mm: Combine the SMP and UP TLB flush code
  riscv: Only send remote fences when some other CPU is online
  riscv: mm: Broadcast kernel TLB flushes only when needed
  riscv: Use IPIs for remote cache/TLB flushes by default
  riscv: Factor out page table TLB synchronization
  riscv: Flush the instruction cache during SMP bringup
  riscv: hwprobe: export Zihintpause ISA extension
  riscv: misaligned: remove CONFIG_RISCV_M_MODE specific code
  ...
2024-05-22 09:56:00 -07:00
Mike Christie
240a1853b4 kernel: Remove signal hacks for vhost_tasks
This removes the signal/coredump hacks added for vhost_tasks in:

Commit f9010dbdce ("fork, vhost: Use CLONE_THREAD to fix freezer/ps regression")

When that patch was added vhost_tasks did not handle SIGKILL and would
try to ignore/clear the signal and continue on until the device's close
function was called. In the previous patches vhost_tasks and the vhost
drivers were converted to support SIGKILL by cleaning themselves up and
exiting. The hacks are no longer needed so this removes them.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20240316004707.45557-10-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-05-22 08:31:15 -04:00
Mike Christie
db5247d9bf vhost_task: Handle SIGKILL by flushing work and exiting
Instead of lingering until the device is closed, this has us handle
SIGKILL by:

1. marking the worker as killed so we no longer try to use it with
   new virtqueues and new flush operations.
2. setting the virtqueue to worker mapping so no new works are queued.
3. running all the exiting works.

Suggested-by: Edward Adam Davis <eadavis@qq.com>
Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com
Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20240316004707.45557-9-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-05-22 08:31:15 -04:00
Yang Li
1e8b7b3dbb rv: Update rv_en(dis)able_monitor doc to match kernel-doc
The patch updates the function documentation comment for
rv_en(dis)able_monitor to adhere to the kernel-doc specification.

Link: https://lore.kernel.org/linux-trace-kernel/20240520054239.61784-1-yang.lee@linux.alibaba.com

Fixes: 102227b970 ("rv: Add Runtime Verification (RV) interface")
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-05-21 19:03:35 -04:00
Jeff Johnson
23748e3e0f tracing: Add MODULE_DESCRIPTION() to preemptirq_delay_test
Fix the 'make W=1' warning:

WARNING: modpost: missing MODULE_DESCRIPTION() in kernel/trace/preemptirq_delay_test.o

Link: https://lore.kernel.org/linux-trace-kernel/20240518-md-preemptirq_delay_test-v1-1-387d11b30d85@quicinc.com

Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: f96e8577da ("lib: Add module for testing preemptoff/irqsoff latency tracers")
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-05-21 19:03:35 -04:00
Petr Pavlu
c2274b908d ring-buffer: Fix a race between readers and resize checks
The reader code in rb_get_reader_page() swaps a new reader page into the
ring buffer by doing cmpxchg on old->list.prev->next to point it to the
new page. Following that, if the operation is successful,
old->list.next->prev gets updated too. This means the underlying
doubly-linked list is temporarily inconsistent, page->prev->next or
page->next->prev might not be equal back to page for some page in the
ring buffer.

The resize operation in ring_buffer_resize() can be invoked in parallel.
It calls rb_check_pages() which can detect the described inconsistency
and stop further tracing:

[  190.271762] ------------[ cut here ]------------
[  190.271771] WARNING: CPU: 1 PID: 6186 at kernel/trace/ring_buffer.c:1467 rb_check_pages.isra.0+0x6a/0xa0
[  190.271789] Modules linked in: [...]
[  190.271991] Unloaded tainted modules: intel_uncore_frequency(E):1 skx_edac(E):1
[  190.272002] CPU: 1 PID: 6186 Comm: cmd.sh Kdump: loaded Tainted: G            E      6.9.0-rc6-default #5 158d3e1e6d0b091c34c3b96bfd99a1c58306d79f
[  190.272011] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552c-rebuilt.opensuse.org 04/01/2014
[  190.272015] RIP: 0010:rb_check_pages.isra.0+0x6a/0xa0
[  190.272023] Code: [...]
[  190.272028] RSP: 0018:ffff9c37463abb70 EFLAGS: 00010206
[  190.272034] RAX: ffff8eba04b6cb80 RBX: 0000000000000007 RCX: ffff8eba01f13d80
[  190.272038] RDX: ffff8eba01f130c0 RSI: ffff8eba04b6cd00 RDI: ffff8eba0004c700
[  190.272042] RBP: ffff8eba0004c700 R08: 0000000000010002 R09: 0000000000000000
[  190.272045] R10: 00000000ffff7f52 R11: ffff8eba7f600000 R12: ffff8eba0004c720
[  190.272049] R13: ffff8eba00223a00 R14: 0000000000000008 R15: ffff8eba067a8000
[  190.272053] FS:  00007f1bd64752c0(0000) GS:ffff8eba7f680000(0000) knlGS:0000000000000000
[  190.272057] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  190.272061] CR2: 00007f1bd6662590 CR3: 000000010291e001 CR4: 0000000000370ef0
[  190.272070] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  190.272073] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  190.272077] Call Trace:
[  190.272098]  <TASK>
[  190.272189]  ring_buffer_resize+0x2ab/0x460
[  190.272199]  __tracing_resize_ring_buffer.part.0+0x23/0xa0
[  190.272206]  tracing_resize_ring_buffer+0x65/0x90
[  190.272216]  tracing_entries_write+0x74/0xc0
[  190.272225]  vfs_write+0xf5/0x420
[  190.272248]  ksys_write+0x67/0xe0
[  190.272256]  do_syscall_64+0x82/0x170
[  190.272363]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[  190.272373] RIP: 0033:0x7f1bd657d263
[  190.272381] Code: [...]
[  190.272385] RSP: 002b:00007ffe72b643f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[  190.272391] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f1bd657d263
[  190.272395] RDX: 0000000000000002 RSI: 0000555a6eb538e0 RDI: 0000000000000001
[  190.272398] RBP: 0000555a6eb538e0 R08: 000000000000000a R09: 0000000000000000
[  190.272401] R10: 0000555a6eb55190 R11: 0000000000000246 R12: 00007f1bd6662500
[  190.272404] R13: 0000000000000002 R14: 00007f1bd6667c00 R15: 0000000000000002
[  190.272412]  </TASK>
[  190.272414] ---[ end trace 0000000000000000 ]---

Note that ring_buffer_resize() calls rb_check_pages() only if the parent
trace_buffer has recording disabled. Recent commit d78ab79270
("tracing: Stop current tracer when resizing buffer") causes that it is
now always the case which makes it more likely to experience this issue.

The window to hit this race is nonetheless very small. To help
reproducing it, one can add a delay loop in rb_get_reader_page():

 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
 if (!ret)
 	goto spin;
 for (unsigned i = 0; i < 1U << 26; i++)  /* inserted delay loop */
 	__asm__ __volatile__ ("" : : : "memory");
 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;

.. and then run the following commands on the target system:

 echo 1 > /sys/kernel/tracing/events/sched/sched_switch/enable
 while true; do
 	echo 16 > /sys/kernel/tracing/buffer_size_kb; sleep 0.1
 	echo 8 > /sys/kernel/tracing/buffer_size_kb; sleep 0.1
 done &
 while true; do
 	for i in /sys/kernel/tracing/per_cpu/*; do
 		timeout 0.1 cat $i/trace_pipe; sleep 0.2
 	done
 done

To fix the problem, make sure ring_buffer_resize() doesn't invoke
rb_check_pages() concurrently with a reader operating on the same
ring_buffer_per_cpu by taking its cpu_buffer->reader_lock.

Link: https://lore.kernel.org/linux-trace-kernel/20240517134008.24529-3-petr.pavlu@suse.com

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: 659f451ff2 ("ring-buffer: Add integrity check at end of iter read")
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
[ Fixed whitespace ]
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-05-21 19:03:35 -04:00
Petr Pavlu
ea70a9628e ring-buffer: Correct stale comments related to non-consuming readers
Adjust the following code documentation:

* Kernel-doc comments for ring_buffer_read_prepare() and
  ring_buffer_read_finish() mention that recording to the ring buffer is
  disabled when the read is active. Remove mention of this restriction
  because it was already lifted in commit 1039221cc2 ("ring-buffer: Do
  not disable recording when there is an iterator").

* Function ring_buffer_read_finish() performs a self-check of the
  ring-buffer by locking cpu_buffer->reader_lock and then calling
  rb_check_pages(). The preceding comment explains that the lock is
  needed because rb_check_pages() clears the HEAD flag required by
  readers which might be running in parallel. Remove this explanation
  because commit 8843e06f67 ("ring-buffer: Handle race between
  rb_move_tail and rb_check_pages") simplified the function so it no
  longer resets the mentioned flag. Nonetheless, the lock is still
  needed because a reader swapping a page into the ring buffer can make
  the underlying doubly-linked list temporarily inconsistent.

This is a non-functional change.

Link: https://lore.kernel.org/linux-trace-kernel/20240517134008.24529-2-petr.pavlu@suse.com

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-05-21 19:03:35 -04:00
Linus Torvalds
4865a27c66 Merge tag 'bitmap-for-6.10v2' of https://github.com/norov/linux
Pull bitmap updates from Yury Norov:

 - topology_span_sane() optimization from Kyle Meyer

 - fns() rework from Kuan-Wei Chiu (used in cpumask_local_spread() and
   other places)

 - headers cleanup from Andy

 - add a MAINTAINERS record for bitops API

* tag 'bitmap-for-6.10v2' of https://github.com/norov/linux:
  usercopy: Don't use "proxy" headers
  bitops: Move aligned_byte_mask() to wordpart.h
  MAINTAINERS: add BITOPS API record
  bitmap: relax find_nth_bit() limitation on return value
  lib: make test_bitops compilable into the kernel image
  bitops: Optimize fns() for improved performance
  lib/test_bitops: Add benchmark test for fns()
  Compiler Attributes: Add __always_used macro
  sched/topology: Optimize topology_span_sane()
  cpumask: Add for_each_cpu_from()
2024-05-21 15:29:01 -07:00