Patch series "mm/damon: Fix fake /proc/loadavg reports", v3.
This patchset fixes DAMON's fake load report issue. The first patch
makes yet another variant of usleep_range() for this fix, and the second
patch fixes the issue of DAMON by making it using the newly introduced
function.
This patch (of 2):
Some kernel threads such as DAMON could need to repeatedly sleep in
micro seconds level. Because usleep_range() sleeps in uninterruptible
state, however, such threads would make /proc/loadavg reports fake load.
To help such cases, this commit implements a variant of usleep_range()
called usleep_idle_range(). It is same to usleep_range() but sets the
state of the current task as TASK_IDLE while sleeping.
Link: https://lkml.kernel.org/r/20211126145015.15862-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20211126145015.15862-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: John Stultz <john.stultz@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
syzbot reported KCSAN data races vs. timer_base::timer_running being set to
NULL without holding base::lock in expire_timers().
This looks innocent and most reads are clearly not problematic, but
Frederic identified an issue which is:
int data = 0;
void timer_func(struct timer_list *t)
{
data = 1;
}
CPU 0 CPU 1
------------------------------ --------------------------
base = lock_timer_base(timer, &flags); raw_spin_unlock(&base->lock);
if (base->running_timer != timer) call_timer_fn(timer, fn, baseclk);
ret = detach_if_pending(timer, base, true); base->running_timer = NULL;
raw_spin_unlock_irqrestore(&base->lock, flags); raw_spin_lock(&base->lock);
x = data;
If the timer has previously executed on CPU 1 and then CPU 0 can observe
base->running_timer == NULL and returns, assuming the timer has completed,
but it's not guaranteed on all architectures. The comment for
del_timer_sync() makes that guarantee. Moving the assignment under
base->lock prevents this.
For non-RT kernel it's performance wise completely irrelevant whether the
store happens before or after taking the lock. For an RT kernel moving the
store under the lock requires an extra unlock/lock pair in the case that
there is a waiter for the timer, but that's not the end of the world.
Reported-by: syzbot+aa7c2385d46c5eba0b89@syzkaller.appspotmail.com
Reported-by: syzbot+abea4558531bae1ba9fe@syzkaller.appspotmail.com
Fixes: 030dcdd197 ("timers: Prepare support for PREEMPT_RT")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/87lfea7gw8.fsf@nanos.tec.linutronix.de
Cc: stable@vger.kernel.org
31cd0e119d ("timers: Recalculate next timer interrupt only when
necessary") subtly altered get_next_timer_interrupt()'s behaviour. The
function no longer consistently returns KTIME_MAX with no timers
pending.
In order to decide if there are any timers pending we check whether the
next expiry will happen NEXT_TIMER_MAX_DELTA jiffies from now.
Unfortunately, the next expiry time and the timer base clock are no
longer updated in unison. The former changes upon certain timer
operations (enqueue, expire, detach), whereas the latter keeps track of
jiffies as they move forward. Ultimately breaking the logic above.
A simplified example:
- Upon entering get_next_timer_interrupt() with:
jiffies = 1
base->clk = 0;
base->next_expiry = NEXT_TIMER_MAX_DELTA;
'base->next_expiry == base->clk + NEXT_TIMER_MAX_DELTA', the function
returns KTIME_MAX.
- 'base->clk' is updated to the jiffies value.
- The next time we enter get_next_timer_interrupt(), taking into account
no timer operations happened:
base->clk = 1;
base->next_expiry = NEXT_TIMER_MAX_DELTA;
'base->next_expiry != base->clk + NEXT_TIMER_MAX_DELTA', the function
returns a valid expire time, which is incorrect.
This ultimately might unnecessarily rearm sched's timer on nohz_full
setups, and add latency to the system[1].
So, introduce 'base->timers_pending'[2], update it every time
'base->next_expiry' changes, and use it in get_next_timer_interrupt().
[1] See tick_nohz_stop_tick().
[2] A quick pahole check on x86_64 and arm64 shows it doesn't make
'struct timer_base' any bigger.
Fixes: 31cd0e119d ("timers: Recalculate next timer interrupt only when necessary")
Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Pull RCU updates from Paul McKenney:
- Bitmap parsing support for "all" as an alias for all bits
- Documentation updates
- Miscellaneous fixes, including some that overlap into mm and lockdep
- kvfree_rcu() updates
- mem_dump_obj() updates, with acks from one of the slab-allocator
maintainers
- RCU NOCB CPU updates, including limited deoffloading
- SRCU updates
- Tasks-RCU updates
- Torture-test updates
* 'core-rcu-2021.07.04' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (78 commits)
tasks-rcu: Make show_rcu_tasks_gp_kthreads() be static inline
rcu-tasks: Make ksoftirqd provide RCU Tasks quiescent states
rcu: Add missing __releases() annotation
rcu: Remove obsolete rcu_read_unlock() deadlock commentary
rcu: Improve comments describing RCU read-side critical sections
rcu: Create an unrcu_pointer() to remove __rcu from a pointer
srcu: Early test SRCU polling start
rcu: Fix various typos in comments
rcu/nocb: Unify timers
rcu/nocb: Prepare for fine-grained deferred wakeup
rcu/nocb: Only cancel nocb timer if not polling
rcu/nocb: Delete bypass_timer upon nocb_gp wakeup
rcu/nocb: Cancel nocb_timer upon nocb_gp wakeup
rcu/nocb: Allow de-offloading rdp leader
rcu/nocb: Directly call __wake_nocb_gp() from bypass timer
rcu: Don't penalize priority boosting when there is nothing to boost
rcu: Point to documentation of ordering guarantees
rcu: Make rcu_gp_cleanup() be noinline for tracing
rcu: Restrict RCU_STRICT_GRACE_PERIOD to at most four CPUs
rcu: Make show_rcu_gp_kthreads() dump rcu_node structures blocking GP
...
This commit addresses a few code-style nits in callback-offloading
toggling, including one that predates this toggling.
Cc: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Pull timers and timekeeping updates from Thomas Gleixner:
"Core:
- Robustness improvements for the NOHZ tick management
- Fixes and consolidation of the NTP/RTC synchronization code
- Small fixes and improvements in various places
- A set of function documentation udpates and fixes
Drivers:
- Cleanups and improvements in various clocksoure/event drivers
- Removal of the EZChip NPS clocksource driver as the platfrom
support was removed from ARC
- The usual set of new device tree binding and json conversions
- The RTC driver which have been acked by the RTC maintainer:
* fix a long standing bug in the MC146818 library code which can
cause reading garbage during the RTC internal update.
* changes related to the NTP/RTC consolidation work"
* tag 'timers-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (46 commits)
ntp: Fix prototype in the !CONFIG_GENERIC_CMOS_UPDATE case
tick/sched: Make jiffies update quick check more robust
ntp: Consolidate the RTC update implementation
ntp: Make the RTC sync offset less obscure
ntp, rtc: Move rtc_set_ntp_time() to ntp code
ntp: Make the RTC synchronization more reliable
rtc: core: Make the sync offset default more realistic
rtc: cmos: Make rtc_cmos sync offset correct
rtc: mc146818: Reduce spinlock section in mc146818_set_time()
rtc: mc146818: Prevent reading garbage
clocksource/drivers/sh_cmt: Fix potential deadlock when calling runtime PM
clocksource/drivers/arm_arch_timer: Correct fault programming of CNTKCTL_EL1.EVNTI
clocksource/drivers/arm_arch_timer: Use stable count reader in erratum sne
clocksource/drivers/dw_apb_timer_of: Add error handling if no clock available
clocksource/drivers/riscv: Make RISCV_TIMER depends on RISCV_SBI
clocksource/drivers/ingenic: Fix section mismatch
clocksource/drivers/cadence_ttc: Fix memory leak in ttc_setup_clockevent()
dt-bindings: timer: renesas: tmu: Convert to json-schema
dt-bindings: timer: renesas: tmu: Document r8a774e1 bindings
clocksource/drivers/orion: Add missing clk_disable_unprepare() on error path
...
No users outside of the timer code. Move the caller below this function to
avoid a pointless forward declaration.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
PREEMPT_RT does not spin and wait until a running timer completes its
callback but instead it blocks on a sleeping lock to prevent a livelock in
the case that the task waiting for the callback completion preempted the
callback.
This cannot be done for timers flagged with TIMER_IRQSAFE. These timers can
be canceled from an interrupt disabled context even on RT kernels.
The expiry callback of such timers is invoked with interrupts disabled so
there is no need to use the expiry lock mechanism because obviously the
callback cannot be preempted even on RT kernels.
Do not use the timer_base::expiry_lock mechanism when waiting for a running
callback to complete if the timer is flagged with TIMER_IRQSAFE.
Also add a lockdep assertion for RT kernels to validate that the expiry
lock mechanism is always invoked in preemptible context.
Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201103190937.hga67rqhvknki3tp@linutronix.de
With the removal of the interrupt perturbations in previous random32
change (random32: make prandom_u32() output unpredictable), the PRNG
has become 100% deterministic again. While SipHash is expected to be
way more robust against brute force than the previous Tausworthe LFSR,
there's still the risk that whoever has even one temporary access to
the PRNG's internal state is able to predict all subsequent draws till
the next reseed (roughly every minute). This may happen through a side
channel attack or any data leak.
This patch restores the spirit of commit f227e3ec3b ("random32: update
the net random state on interrupt and activity") in that it will perturb
the internal PRNG's statee using externally collected noise, except that
it will not pick that noise from the random pool's bits nor upon
interrupt, but will rather combine a few elements along the Tx path
that are collectively hard to predict, such as dev, skb and txq
pointers, packet length and jiffies values. These ones are combined
using a single round of SipHash into a single long variable that is
mixed with the net_rand_state upon each invocation.
The operation was inlined because it produces very small and efficient
code, typically 3 xor, 2 add and 2 rol. The performance was measured
to be the same (even very slightly better) than before the switch to
SipHash; on a 6-core 12-thread Core i7-8700k equipped with a 40G NIC
(i40e), the connection rate dropped from 556k/s to 555k/s while the
SYN cookie rate grew from 5.38 Mpps to 5.45 Mpps.
Link: https://lore.kernel.org/netdev/20200808152628.GA27941@SDF.ORG/
Cc: George Spelvin <lkml@sdf.org>
Cc: Amit Klein <aksecurity@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: tytso@mit.edu
Cc: Florian Westphal <fw@strlen.de>
Cc: Marc Plumb <lkml.mplumb@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Non-cryptographic PRNGs may have great statistical properties, but
are usually trivially predictable to someone who knows the algorithm,
given a small sample of their output. An LFSR like prandom_u32() is
particularly simple, even if the sample is widely scattered bits.
It turns out the network stack uses prandom_u32() for some things like
random port numbers which it would prefer are *not* trivially predictable.
Predictability led to a practical DNS spoofing attack. Oops.
This patch replaces the LFSR with a homebrew cryptographic PRNG based
on the SipHash round function, which is in turn seeded with 128 bits
of strong random key. (The authors of SipHash have *not* been consulted
about this abuse of their algorithm.) Speed is prioritized over security;
attacks are rare, while performance is always wanted.
Replacing all callers of prandom_u32() is the quick fix.
Whether to reinstate a weaker PRNG for uses which can tolerate it
is an open question.
Commit f227e3ec3b ("random32: update the net random state on interrupt
and activity") was an earlier attempt at a solution. This patch replaces
it.
Reported-by: Amit Klein <aksecurity@gmail.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: tytso@mit.edu
Cc: Florian Westphal <fw@strlen.de>
Cc: Marc Plumb <lkml.mplumb@gmail.com>
Fixes: f227e3ec3b ("random32: update the net random state on interrupt and activity")
Signed-off-by: George Spelvin <lkml@sdf.org>
Link: https://lore.kernel.org/netdev/20200808152628.GA27941@SDF.ORG/
[ willy: partial reversal of f227e3ec3b5c; moved SIPROUND definitions
to prandom.h for later use; merged George's prandom_seed() proposal;
inlined siprand_u32(); replaced the net_rand_state[] array with 4
members to fix a build issue; cosmetic cleanups to make checkpatch
happy; fixed RANDOM32_SELFTEST build ]
Signed-off-by: Willy Tarreau <w@1wt.eu>
Pull timekeeping updates from Thomas Gleixner:
"Updates for timekeeping, timers and related drivers:
Core:
- Early boot support for the NMI safe timekeeper by utilizing
local_clock() up to the point where timekeeping is initialized.
This allows printk() to store multiple timestamps in the ringbuffer
which is useful for coordinating dmesg information across a fleet
of machines.
- Provide a multi-timestamp accessor for printk()
- Make timer init more robust by checking for invalid timer flags.
- Comma vs semicolon fixes
Drivers:
- Support for new platforms in existing drivers (SP804 and Renesas
CMT)
- Comma vs semicolon fixes
* tag 'timers-core-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
clocksource/drivers/armada-370-xp: Use semicolons rather than commas to separate statements
clocksource/drivers/mps2-timer: Use semicolons rather than commas to separate statements
timers: Mask invalid flags in do_init_timer()
clocksource/drivers/sp804: Enable Hisilicon sp804 timer 64bit mode
clocksource/drivers/sp804: Add support for Hisilicon sp804 timer
clocksource/drivers/sp804: Support non-standard register offset
clocksource/drivers/sp804: Prepare for support non-standard register offset
clocksource/drivers/sp804: Remove a mismatched comment
clocksource/drivers/sp804: Delete the leading "__" of some functions
clocksource/drivers/sp804: Remove unused sp804_timer_disable() and timer-sp804.h
clocksource/drivers/sp804: Cleanup clk_get_sys()
dt-bindings: timer: renesas,cmt: Document r8a774e1 CMT support
dt-bindings: timer: renesas,cmt: Document r8a7742 CMT support
alarmtimer: Convert comma to semicolon
timekeeping: Provide multi-timestamp accessor to NMI safe timekeeper
timekeeping: Utilize local_clock() for NMI safe timekeeper during early boot
do_init_timer() accepts any combination of timer flags handed in by the
caller without a sanity check, but only TIMER_DEFFERABLE, TIMER_PINNED and
TIMER_IRQSAFE are valid.
If the supplied flags have other bits set, this could result in
malfunction. If bits are set in TIMER_CPUMASK the first timer usage could
deference a cpu base which is outside the range of possible CPUs. If
TIMER_MIGRATION is set, then the switch_timer_base() will live lock.
Prevent that with a sanity check which warns when invalid flags are
supplied and masks them out.
[ tglx: Made it WARN_ON_ONCE() and added context to the changelog ]
Signed-off-by: Qianli Zhao <zhaoqianli@xiaomi.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/9d79a8aa4eb56713af7379f99f062dedabcde140.1597326756.git.zhaoqianli@xiaomi.com
Running posix CPU timers in hard interrupt context has a few downsides:
- For PREEMPT_RT it cannot work as the expiry code needs to take
sighand lock, which is a 'sleeping spinlock' in RT. The original RT
approach of offloading the posix CPU timer handling into a high
priority thread was clumsy and provided no real benefit in general.
- For fine grained accounting it's just wrong to run this in context of
the timer interrupt because that way a process specific CPU time is
accounted to the timer interrupt.
- Long running timer interrupts caused by a large amount of expiring
timers which can be created and armed by unpriviledged user space.
There is no hard requirement to expire them in interrupt context.
If the signal is targeted at the task itself then it won't be delivered
before the task returns to user space anyway. If the signal is targeted at
a supervisor process then it might be slightly delayed, but posix CPU
timers are inaccurate anyway due to the fact that they are tied to the
tick.
Provide infrastructure to schedule task work which allows splitting the
posix CPU timer code into a quick check in interrupt context and a thread
context expiry and signal delivery function. This has to be enabled by
architectures as it requires that the architecture specific KVM
implementation handles pending task work before exiting to guest mode.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200730102337.783470146@linutronix.de
Pull timer updates from Thomas Gleixner:
"Time, timers and related driver updates:
- Prevent unnecessary timer softirq invocations by extending the
tracking of the next expiring timer in the timer wheel beyond the
existing NOHZ functionality.
The tracking overhead at enqueue time is within the noise, but on
sensitive workloads the avoidance of the soft interrupt invocation
is a measurable improvement.
- The obligatory new clocksource driver for Ingenic X100 OST
- The usual fixes, improvements, cleanups and extensions for newer
chip variants all over the driver space"
* tag 'timers-core-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (28 commits)
timers: Recalculate next timer interrupt only when necessary
clocksource/drivers/ingenic: Add support for the Ingenic X1000 OST.
dt-bindings: timer: Add Ingenic X1000 OST bindings.
clocksource/drivers: Replace HTTP links with HTTPS ones
clocksource/drivers/nomadik-mtu: Handle 32kHz clock
clocksource/drivers/sh_cmt: Use "kHz" for kilohertz
clocksource/drivers/imx: Add support for i.MX TPM driver with ARM64
clocksource/drivers/ingenic: Add high resolution timer support for SMP/SMT.
timers: Lower base clock forwarding threshold
timers: Remove must_forward_clk
timers: Spare timer softirq until next expiry
timers: Expand clk forward logic beyond nohz
timers: Reuse next expiry cache after nohz exit
timers: Always keep track of next expiry
timers: Optimize _next_timer_interrupt() level iteration
timers: Add comments about calc_index() ceiling work
timers: Move trigger_dyntick_cpu() to enqueue_timer()
timers: Use only bucket expiry for base->next_expiry value
timers: Preserve higher bits of expiration on index calculation
clocksource/drivers/timer-atmel-tcb: Add sama5d2 support
...
This modifies the first 32 bits out of the 128 bits of a random CPU's
net_rand_state on interrupt or CPU activity to complicate remote
observations that could lead to guessing the network RNG's internal
state.
Note that depending on some network devices' interrupt rate moderation
or binding, this re-seeding might happen on every packet or even almost
never.
In addition, with NOHZ some CPUs might not even get timer interrupts,
leaving their local state rarely updated, while they are running
networked processes making use of the random state. For this reason, we
also perform this update in update_process_times() in order to at least
update the state when there is user or system activity, since it's the
only case we care about.
Reported-by: Amit Klein <aksecurity@gmail.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The nohz tick code recalculates the timer wheel's next expiry on each idle
loop iteration.
On the other hand, the base next expiry is now always cached and updated
upon timer enqueue and execution. Only timer dequeue may leave
base->next_expiry out of date (but then its stale value won't ever go past
the actual next expiry to be recalculated).
Since recalculating the next_expiry isn't a free operation, especially when
the last wheel level is reached to find out that no timer has been enqueued
at all, reuse the next expiry cache when it is known to be reliable, which
it is most of the time.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200723151641.12236-1-frederic@kernel.org
