Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
* [tip: core/rcu] mm/mmap.c: Add cond_resched() for exit_mmap() CPU stalls
@ 2020-07-31  9:23 tip-bot2 for Paul E. McKenney
  0 siblings, 0 replies; only message in thread
From: tip-bot2 for Paul E. McKenney @ 2020-07-31  9:23 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Andrew Morton, linux-mm, Shakeel Butt, Joel Fernandes (Google),
	Paul E. McKenney, x86, LKML

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     0a3b3c253a1eb2c7fe7f34086d46660c909abeb3
Gitweb:        https://git.kernel.org/tip/0a3b3c253a1eb2c7fe7f34086d46660c909abeb3
Author:        Paul E. McKenney <paulmck@kernel.org>
AuthorDate:    Thu, 16 Apr 2020 16:46:10 -07:00
Committer:     Paul E. McKenney <paulmck@kernel.org>
CommitterDate: Mon, 29 Jun 2020 11:58:49 -07:00

mm/mmap.c: Add cond_resched() for exit_mmap() CPU stalls

A large process running on a heavily loaded system can encounter the
following RCU CPU stall warning:

  rcu: INFO: rcu_sched self-detected stall on CPU
  rcu: 	3-....: (20998 ticks this GP) idle=4ea/1/0x4000000000000002 softirq=556558/556558 fqs=5190
  	(t=21013 jiffies g=1005461 q=132576)
  NMI backtrace for cpu 3
  CPU: 3 PID: 501900 Comm: aio-free-ring-w Kdump: loaded Not tainted 5.2.9-108_fbk12_rc3_3858_gb83b75af7909 #1
  Hardware name: Wiwynn   HoneyBadger/PantherPlus, BIOS HBM6.71 02/03/2016
  Call Trace:
   <IRQ>
   dump_stack+0x46/0x60
   nmi_cpu_backtrace.cold.3+0x13/0x50
   ? lapic_can_unplug_cpu.cold.27+0x34/0x34
   nmi_trigger_cpumask_backtrace+0xba/0xca
   rcu_dump_cpu_stacks+0x99/0xc7
   rcu_sched_clock_irq.cold.87+0x1aa/0x397
   ? tick_sched_do_timer+0x60/0x60
   update_process_times+0x28/0x60
   tick_sched_timer+0x37/0x70
   __hrtimer_run_queues+0xfe/0x270
   hrtimer_interrupt+0xf4/0x210
   smp_apic_timer_interrupt+0x5e/0x120
   apic_timer_interrupt+0xf/0x20
   </IRQ>
  RIP: 0010:kmem_cache_free+0x223/0x300
  Code: 88 00 00 00 0f 85 ca 00 00 00 41 8b 55 18 31 f6 f7 da 41 f6 45 0a 02 40 0f 94 c6 83 c6 05 9c 41 5e fa e8 a0 a7 01 00 41 56 9d <49> 8b 47 08 a8 03 0f 85 87 00 00 00 65 48 ff 08 e9 3d fe ff ff 65
  RSP: 0018:ffffc9000e8e3da8 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13
  RAX: 0000000000020000 RBX: ffff88861b9de960 RCX: 0000000000000030
  RDX: fffffffffffe41e8 RSI: 000060777fe3a100 RDI: 000000000001be18
  RBP: ffffea00186e7780 R08: ffffffffffffffff R09: ffffffffffffffff
  R10: ffff88861b9dea28 R11: ffff88887ffde000 R12: ffffffff81230a1f
  R13: ffff888854684dc0 R14: 0000000000000206 R15: ffff8888547dbc00
   ? remove_vma+0x4f/0x60
   remove_vma+0x4f/0x60
   exit_mmap+0xd6/0x160
   mmput+0x4a/0x110
   do_exit+0x278/0xae0
   ? syscall_trace_enter+0x1d3/0x2b0
   ? handle_mm_fault+0xaa/0x1c0
   do_group_exit+0x3a/0xa0
   __x64_sys_exit_group+0x14/0x20
   do_syscall_64+0x42/0x100
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

And on a PREEMPT=n kernel, the "while (vma)" loop in exit_mmap() can run
for a very long time given a large process.  This commit therefore adds
a cond_resched() to this loop, providing RCU any needed quiescent states.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <linux-mm@kvack.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 mm/mmap.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/mmap.c b/mm/mmap.c
index 59a4682..972f839 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3159,6 +3159,7 @@ void exit_mmap(struct mm_struct *mm)
 		if (vma->vm_flags & VM_ACCOUNT)
 			nr_accounted += vma_pages(vma);
 		vma = remove_vma(vma);
+		cond_resched();
 	}
 	vm_unacct_memory(nr_accounted);
 }


^ permalink raw reply	[flat|nested] only message in thread

only message in thread, back to index

Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-07-31  9:23 [tip: core/rcu] mm/mmap.c: Add cond_resched() for exit_mmap() CPU stalls tip-bot2 for Paul E. McKenney

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org
	public-inbox-index linux-mm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git