Pull timer/dynticks updates from Ingo Molnar:
"This tree contains misc dynticks updates: a fix and three cleanups"
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/nohz: Fix overflow error in scheduler_tick_max_deferment()
nohz_full: fix code style issue of tick_nohz_full_stop_tick
nohz: Get timekeeping max deferment outside jiffies_lock
tick: Rename tick_check_idle() to tick_irq_enter()
Pull scheduler changes from Ingo Molnar:
- Add the initial implementation of SCHED_DEADLINE support: a real-time
scheduling policy where tasks that meet their deadlines and
periodically execute their instances in less than their runtime quota
see real-time scheduling and won't miss any of their deadlines.
Tasks that go over their quota get delayed (Available to privileged
users for now)
- Clean up and fix preempt_enable_no_resched() abuse all around the
tree
- Do sched_clock() performance optimizations on x86 and elsewhere
- Fix and improve auto-NUMA balancing
- Fix and clean up the idle loop
- Apply various cleanups and fixes
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (60 commits)
sched: Fix __sched_setscheduler() nice test
sched: Move SCHED_RESET_ON_FORK into attr::sched_flags
sched: Fix up attr::sched_priority warning
sched: Fix up scheduler syscall LTP fails
sched: Preserve the nice level over sched_setscheduler() and sched_setparam() calls
sched/core: Fix htmldocs warnings
sched/deadline: No need to check p if dl_se is valid
sched/deadline: Remove unused variables
sched/deadline: Fix sparse static warnings
m68k: Fix build warning in mac_via.h
sched, thermal: Clean up preempt_enable_no_resched() abuse
sched, net: Fixup busy_loop_us_clock()
sched, net: Clean up preempt_enable_no_resched() abuse
sched/preempt: Fix up missed PREEMPT_NEED_RESCHED folding
sched/preempt, locking: Rework local_bh_{dis,en}able()
sched/clock, x86: Avoid a runtime condition in native_sched_clock()
sched/clock: Fix up clear_sched_clock_stable()
sched/clock, x86: Use a static_key for sched_clock_stable
sched/clock: Remove local_irq_disable() from the clocks
sched/clock, x86: Rewrite cyc2ns() to avoid the need to disable IRQs
...
Currently all _bh_ lock functions do two preempt_count operations:
local_bh_disable();
preempt_disable();
and for the unlock:
preempt_enable_no_resched();
local_bh_enable();
Since its a waste of perfectly good cycles to modify the same variable
twice when you can do it in one go; use the new
__local_bh_{dis,en}able_ip() functions that allow us to provide a
preempt_count value to add/sub.
So define SOFTIRQ_LOCK_OFFSET as the offset a _bh_ lock needs to
add/sub to be done in one go.
As a bonus it gets rid of the preempt_enable_no_resched() usage.
This reduces a 1000 loops of:
spin_lock_bh(&bh_lock);
spin_unlock_bh(&bh_lock);
from 53596 cycles to 51995 cycles. I didn't do enough measurements to
say for absolute sure that the result is significant but the the few
runs I did for each suggest it is so.
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: jacob.jun.pan@linux.intel.com
Cc: Mike Galbraith <bitbucket@online.de>
Cc: hpa@zytor.com
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: lenb@kernel.org
Cc: rjw@rjwysocki.net
Cc: rui.zhang@intel.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20131119151338.GF3694@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
A few functions use remote per CPU access APIs when they
deal with local values.
Just do the right conversion to improve performance, code
readability and debug checks.
While at it, lets extend some of these function names with *_this_cpu()
suffix in order to display their purpose more clearly.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
There was a reported deadlock on -rt which lockdep didn't report.
It turns out that in irq_exit() we tell lockdep that the hardirq
context ends and then do all kinds of locking afterwards.
To fix it, move trace_hardirq_exit() to the very end of irq_exit(), this
ensures all locking in tick_irq_exit() and rcu_irq_exit() are properly
recorded as happening from hardirq context.
This however leads to the 'fun' little problem of running softirqs
while in hardirq context. To cure this make the softirq code a little
more complex (in the CONFIG_TRACE_IRQFLAGS case).
Due to stack swizzling arch dependent trickery we cannot pass an
argument to __do_softirq() to tell it if it was done from hardirq
context or not; so use a side-band argument.
When we do __do_softirq() from hardirq context, 'atomically' flip to
softirq context and back, so that no locking goes without being in
either hard- or soft-irq context.
I didn't find any new problems in mainline using this patch, but it
did show the -rt problem.
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-dgwc5cdksbn0jk09vbmcc9sa@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit was incomplete in that code to remove items from the per-cpu
lists was missing and never acquired a user in the 5 years it has been in
the tree. We're going to implement what it seems to try to archive in a
simpler way, and this code is in the way of doing so.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull scheduler changes from Ingo Molnar:
"The main changes in this cycle are:
- (much) improved CONFIG_NUMA_BALANCING support from Mel Gorman, Rik
van Riel, Peter Zijlstra et al. Yay!
- optimize preemption counter handling: merge the NEED_RESCHED flag
into the preempt_count variable, by Peter Zijlstra.
- wait.h fixes and code reorganization from Peter Zijlstra
- cfs_bandwidth fixes from Ben Segall
- SMP load-balancer cleanups from Peter Zijstra
- idle balancer improvements from Jason Low
- other fixes and cleanups"
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (129 commits)
ftrace, sched: Add TRACE_FLAG_PREEMPT_RESCHED
stop_machine: Fix race between stop_two_cpus() and stop_cpus()
sched: Remove unnecessary iteration over sched domains to update nr_busy_cpus
sched: Fix asymmetric scheduling for POWER7
sched: Move completion code from core.c to completion.c
sched: Move wait code from core.c to wait.c
sched: Move wait.c into kernel/sched/
sched/wait: Fix __wait_event_interruptible_lock_irq_timeout()
sched: Avoid throttle_cfs_rq() racing with period_timer stopping
sched: Guarantee new group-entities always have weight
sched: Fix hrtimer_cancel()/rq->lock deadlock
sched: Fix cfs_bandwidth misuse of hrtimer_expires_remaining
sched: Fix race on toggling cfs_bandwidth_used
sched: Remove extra put_online_cpus() inside sched_setaffinity()
sched/rt: Fix task_tick_rt() comment
sched/wait: Fix build breakage
sched/wait: Introduce prepare_to_wait_event()
sched/wait: Add ___wait_cond_timeout() to wait_event*_timeout() too
sched: Remove get_online_cpus() usage
sched: Fix race in migrate_swap_stop()
...
Merge Linux v3.12-rc4 to fix a conflict and also to refresh the tree
before applying more scheduler patches.
Conflicts:
arch/avr32/include/asm/Kbuild
Signed-off-by: Ingo Molnar <mingo@kernel.org>
If irq_exit() is called on the arch's specified irq stack,
it should be safe to run softirqs inline under that same
irq stack as it is near empty by the time we call irq_exit().
For example if we use the same stack for both hard and soft irqs here,
the worst case scenario is:
hardirq -> softirq -> hardirq. But then the softirq supersedes the
first hardirq as the stack user since irq_exit() is called in
a mostly empty stack. So the stack merge in this case looks acceptable.
Stack overrun still have a chance to happen if hardirqs have more
opportunities to nest, but then it's another problem to solve.
So lets adapt the irq exit's softirq stack on top of a new Kconfig symbol
that can be defined when irq_exit() runs on the irq stack. That way
we can spare some stack switch on irq processing and all the cache
issues that come along.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@au1.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@au1.ibm.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
The commit facd8b80c6
("irq: Sanitize invoke_softirq") converted irq exit
calls of do_softirq() to __do_softirq() on all architectures,
assuming it was only used there for its irq disablement
properties.
But as a side effect, the softirqs processed in the end
of the hardirq are always called on the inline current
stack that is used by irq_exit() instead of the softirq
stack provided by the archs that override do_softirq().
The result is mostly safe if the architecture runs irq_exit()
on a separate irq stack because then softirqs are processed
on that same stack that is near empty at this stage (assuming
hardirq aren't nesting).
Otherwise irq_exit() runs in the task stack and so does the softirq
too. The interrupted call stack can be randomly deep already and
the softirq can dig through it even further. To add insult to the
injury, this softirq can be interrupted by a new hardirq, maximizing
the chances for a stack overrun as reported in powerpc for example:
do_IRQ: stack overflow: 1920
CPU: 0 PID: 1602 Comm: qemu-system-ppc Not tainted 3.10.4-300.1.fc19.ppc64p7 #1
Call Trace:
[c0000000050a8740] .show_stack+0x130/0x200 (unreliable)
[c0000000050a8810] .dump_stack+0x28/0x3c
[c0000000050a8880] .do_IRQ+0x2b8/0x2c0
[c0000000050a8930] hardware_interrupt_common+0x154/0x180
--- Exception: 501 at .cp_start_xmit+0x3a4/0x820 [8139cp]
LR = .cp_start_xmit+0x390/0x820 [8139cp]
[c0000000050a8d40] .dev_hard_start_xmit+0x394/0x640
[c0000000050a8e00] .sch_direct_xmit+0x110/0x260
[c0000000050a8ea0] .dev_queue_xmit+0x260/0x630
[c0000000050a8f40] .br_dev_queue_push_xmit+0xc4/0x130 [bridge]
[c0000000050a8fc0] .br_dev_xmit+0x198/0x270 [bridge]
[c0000000050a9070] .dev_hard_start_xmit+0x394/0x640
[c0000000050a9130] .dev_queue_xmit+0x428/0x630
[c0000000050a91d0] .ip_finish_output+0x2a4/0x550
[c0000000050a9290] .ip_local_out+0x50/0x70
[c0000000050a9310] .ip_queue_xmit+0x148/0x420
[c0000000050a93b0] .tcp_transmit_skb+0x4e4/0xaf0
[c0000000050a94a0] .__tcp_ack_snd_check+0x7c/0xf0
[c0000000050a9520] .tcp_rcv_established+0x1e8/0x930
[c0000000050a95f0] .tcp_v4_do_rcv+0x21c/0x570
[c0000000050a96c0] .tcp_v4_rcv+0x734/0x930
[c0000000050a97a0] .ip_local_deliver_finish+0x184/0x360
[c0000000050a9840] .ip_rcv_finish+0x148/0x400
[c0000000050a98d0] .__netif_receive_skb_core+0x4f8/0xb00
[c0000000050a99d0] .netif_receive_skb+0x44/0x110
[c0000000050a9a70] .br_handle_frame_finish+0x2bc/0x3f0 [bridge]
[c0000000050a9b20] .br_nf_pre_routing_finish+0x2ac/0x420 [bridge]
[c0000000050a9bd0] .br_nf_pre_routing+0x4dc/0x7d0 [bridge]
[c0000000050a9c70] .nf_iterate+0x114/0x130
[c0000000050a9d30] .nf_hook_slow+0xb4/0x1e0
[c0000000050a9e00] .br_handle_frame+0x290/0x330 [bridge]
[c0000000050a9ea0] .__netif_receive_skb_core+0x34c/0xb00
[c0000000050a9fa0] .netif_receive_skb+0x44/0x110
[c0000000050aa040] .napi_gro_receive+0xe8/0x120
[c0000000050aa0c0] .cp_rx_poll+0x31c/0x590 [8139cp]
[c0000000050aa1d0] .net_rx_action+0x1dc/0x310
[c0000000050aa2b0] .__do_softirq+0x158/0x330
[c0000000050aa3b0] .irq_exit+0xc8/0x110
[c0000000050aa430] .do_IRQ+0xdc/0x2c0
[c0000000050aa4e0] hardware_interrupt_common+0x154/0x180
--- Exception: 501 at .bad_range+0x1c/0x110
LR = .get_page_from_freelist+0x908/0xbb0
[c0000000050aa7d0] .list_del+0x18/0x50 (unreliable)
[c0000000050aa850] .get_page_from_freelist+0x908/0xbb0
[c0000000050aa9e0] .__alloc_pages_nodemask+0x21c/0xae0
[c0000000050aaba0] .alloc_pages_vma+0xd0/0x210
[c0000000050aac60] .handle_pte_fault+0x814/0xb70
[c0000000050aad50] .__get_user_pages+0x1a4/0x640
[c0000000050aae60] .get_user_pages_fast+0xec/0x160
[c0000000050aaf10] .__gfn_to_pfn_memslot+0x3b0/0x430 [kvm]
[c0000000050aafd0] .kvmppc_gfn_to_pfn+0x64/0x130 [kvm]
[c0000000050ab070] .kvmppc_mmu_map_page+0x94/0x530 [kvm]
[c0000000050ab190] .kvmppc_handle_pagefault+0x174/0x610 [kvm]
[c0000000050ab270] .kvmppc_handle_exit_pr+0x464/0x9b0 [kvm]
[c0000000050ab320] kvm_start_lightweight+0x1ec/0x1fc [kvm]
[c0000000050ab4f0] .kvmppc_vcpu_run_pr+0x168/0x3b0 [kvm]
[c0000000050ab9c0] .kvmppc_vcpu_run+0xc8/0xf0 [kvm]
[c0000000050aba50] .kvm_arch_vcpu_ioctl_run+0x5c/0x1a0 [kvm]
[c0000000050abae0] .kvm_vcpu_ioctl+0x478/0x730 [kvm]
[c0000000050abc90] .do_vfs_ioctl+0x4ec/0x7c0
[c0000000050abd80] .SyS_ioctl+0xd4/0xf0
[c0000000050abe30] syscall_exit+0x0/0x98
Since this is a regression, this patch proposes a minimalistic
and low-risk solution by blindly forcing the hardirq exit processing of
softirqs on the softirq stack. This way we should reduce significantly
the opportunities for task stack overflow dug by softirqs.
Longer term solutions may involve extending the hardirq stack coverage to
irq_exit(), etc...
Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: #3.9.. <stable@vger.kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@au1.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@au1.ibm.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Rewrite the preempt_count macros in order to extract the 3 basic
preempt_count value modifiers:
__preempt_count_add()
__preempt_count_sub()
and the new:
__preempt_count_dec_and_test()
And since we're at it anyway, replace the unconventional
$op_preempt_count names with the more conventional preempt_count_$op.
Since these basic operators are equivalent to the previous _notrace()
variants, do away with the _notrace() versions.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-ewbpdbupy9xpsjhg960zwbv8@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Replace the single preempt_count() 'function' that's an lvalue with
two proper functions:
preempt_count() - returns the preempt_count value as rvalue
preempt_count_set() - Allows setting the preempt-count value
Also provide preempt_count_ptr() as a convenience wrapper to implement
all modifying operations.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-orxrbycjozopqfhb4dxdkdvb@git.kernel.org
[ Fixed build failure. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
