+ mm-page_alloc-drain-per-cpu-pages-from-workqueue-context-fix.patch added to -mm tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



The patch titled
     Subject: mm, page_alloc: do not depend on cpu hotplug locks inside the allocator
has been added to the -mm tree.  Its filename is
     mm-page_alloc-drain-per-cpu-pages-from-workqueue-context-fix.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-drain-per-cpu-pages-from-workqueue-context-fix.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-drain-per-cpu-pages-from-workqueue-context-fix.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/SubmitChecklist when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Michal Hocko <mhocko@xxxxxxxx>
Subject: mm, page_alloc: do not depend on cpu hotplug locks inside the allocator

Dmitry has reported the following lockdep splat
[<ffffffff81571db1>] lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3753
[<ffffffff8436697e>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
[<ffffffff8436697e>] mutex_lock_nested+0x24e/0xff0 kernel/locking/mutex.c:621
[<ffffffff818f07ea>] pcpu_alloc+0xbda/0x1280 mm/percpu.c:896
[<ffffffff818f0ee4>] __alloc_percpu+0x24/0x30 mm/percpu.c:1075
[<ffffffff816543e3>] smpcfd_prepare_cpu+0x73/0xd0 kernel/smp.c:44
[<ffffffff814240b4>] cpuhp_invoke_callback+0x254/0x1480 kernel/cpu.c:136
[<ffffffff81425821>] cpuhp_up_callbacks+0x81/0x2a0 kernel/cpu.c:493
[<ffffffff81427bf3>] _cpu_up+0x1e3/0x2a0 kernel/cpu.c:1057
[<ffffffff81427d23>] do_cpu_up+0x73/0xa0 kernel/cpu.c:1087
[<ffffffff81427d68>] cpu_up+0x18/0x20 kernel/cpu.c:1095
[<ffffffff854ede84>] smp_init+0xe9/0xee kernel/smp.c:564
[<ffffffff85482f81>] kernel_init_freeable+0x439/0x690 init/main.c:1010
[<ffffffff84357083>] kernel_init+0x13/0x180 init/main.c:941
[<ffffffff84377baa>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433

cpu_hotplug_begin
  cpu_hotplug.lock
pcpu_alloc
  pcpu_alloc_mutex

[<ffffffff81423012>] get_online_cpus+0x62/0x90 kernel/cpu.c:248
[<ffffffff8185fcf8>] drain_all_pages+0xf8/0x710 mm/page_alloc.c:2385
[<ffffffff81865e5d>] __alloc_pages_direct_reclaim mm/page_alloc.c:3440 [inline]
[<ffffffff81865e5d>] __alloc_pages_slowpath+0x8fd/0x2370 mm/page_alloc.c:3778
[<ffffffff818681c5>] __alloc_pages_nodemask+0x8f5/0xc60 mm/page_alloc.c:3980
[<ffffffff818ed0c1>] __alloc_pages include/linux/gfp.h:426 [inline]
[<ffffffff818ed0c1>] __alloc_pages_node include/linux/gfp.h:439 [inline]
[<ffffffff818ed0c1>] alloc_pages_node include/linux/gfp.h:453 [inline]
[<ffffffff818ed0c1>] pcpu_alloc_pages mm/percpu-vm.c:93 [inline]
[<ffffffff818ed0c1>] pcpu_populate_chunk+0x1e1/0x900 mm/percpu-vm.c:282
[<ffffffff818f0a11>] pcpu_alloc+0xe01/0x1280 mm/percpu.c:998
[<ffffffff818f0eb7>] __alloc_percpu_gfp+0x27/0x30 mm/percpu.c:1062
[<ffffffff817d25b2>] bpf_array_alloc_percpu kernel/bpf/arraymap.c:34 [inline]
[<ffffffff817d25b2>] array_map_alloc+0x532/0x710 kernel/bpf/arraymap.c:99
[<ffffffff817ba034>] find_and_alloc_map kernel/bpf/syscall.c:34 [inline]
[<ffffffff817ba034>] map_create kernel/bpf/syscall.c:188 [inline]
[<ffffffff817ba034>] SYSC_bpf kernel/bpf/syscall.c:870 [inline]
[<ffffffff817ba034>] SyS_bpf+0xd64/0x2500 kernel/bpf/syscall.c:827
[<ffffffff84377941>] entry_SYSCALL_64_fastpath+0x1f/0xc2

pcpu_alloc
  pcpu_alloc_mutex
drain_all_pages
  get_online_cpus
    cpu_hotplug.lock

[<ffffffff81427876>] cpu_hotplug_begin+0x206/0x2e0 kernel/cpu.c:304
[<ffffffff81427ada>] _cpu_up+0xca/0x2a0 kernel/cpu.c:1011
[<ffffffff81427d23>] do_cpu_up+0x73/0xa0 kernel/cpu.c:1087
[<ffffffff81427d68>] cpu_up+0x18/0x20 kernel/cpu.c:1095
[<ffffffff854ede84>] smp_init+0xe9/0xee kernel/smp.c:564
[<ffffffff85482f81>] kernel_init_freeable+0x439/0x690 init/main.c:1010
[<ffffffff84357083>] kernel_init+0x13/0x180 init/main.c:941
[<ffffffff84377baa>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433

cpu_hotplug_begin
  cpu_hotplug.lock

Pulling cpu hotplug locks inside the page allocator is just too
dangerous. Let's remove the dependency by dropping get_online_cpus()
from drain_all_pages. This is not so simple though because now we do not
have a protection against cpu hotplug which means 2 things:
	- the work item might be executed on a different cpu in worker
	  from unbound pool so it doesn't run on pinned on the cpu
	- we have to make sure that we do not race with page_alloc_cpu_dead
	  calling drain_pages_zone

Disabling preemption in drain_local_pages_wq will solve the first
problem drain_local_pages will determine its local CPU from the WQ
context which will be stable after that point, page_alloc_cpu_dead
is pinned to the CPU already. The later condition is achieved
by disabling IRQs in drain_pages_zone.

Fixes: mm, page_alloc: drain per-cpu pages from workqueue context
Link: http://lkml.kernel.org/r/20170207201950.20482-1-mhocko@xxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/page_alloc.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff -puN mm/page_alloc.c~mm-page_alloc-drain-per-cpu-pages-from-workqueue-context-fix mm/page_alloc.c
--- a/mm/page_alloc.c~mm-page_alloc-drain-per-cpu-pages-from-workqueue-context-fix
+++ a/mm/page_alloc.c
@@ -2341,7 +2341,16 @@ void drain_local_pages(struct zone *zone
 
 static void drain_local_pages_wq(struct work_struct *work)
 {
+	/*
+	 * drain_all_pages doesn't use proper cpu hotplug protection so
+	 * we can race with cpu offline when the WQ can move this from
+	 * a cpu pinned worker to an unbound one. We can operate on a different
+	 * cpu which is allright but we also have to make sure to not move to
+	 * a different one.
+	 */
+	preempt_disable();
 	drain_local_pages(NULL);
+	preempt_enable();
 }
 
 /*
@@ -2366,11 +2375,6 @@ void drain_all_pages(struct zone *zone)
 	if (current->flags & PF_WQ_WORKER)
 		return;
 
-	/*
-	 * As this can be called from reclaim context, do not reenter reclaim.
-	 * An allocation failure can be handled, it's simply slower
-	 */
-	get_online_cpus();
 	works = alloc_percpu_gfp(struct work_struct, GFP_ATOMIC);
 
 	/*
@@ -2421,7 +2425,6 @@ void drain_all_pages(struct zone *zone)
 			flush_work(&work);
 		}
 	}
-	put_online_cpus();
 }
 
 #ifdef CONFIG_HIBERNATION
_

Patches currently in -mm which might be from mhocko@xxxxxxxx are

mm-throttle-show_mem-from-warn_alloc.patch
mm-trace-extract-compaction_status-and-zone_type-to-a-common-header.patch
oom-trace-add-oom-detection-tracepoints.patch
oom-trace-add-compaction-retry-tracepoint.patch
mm-vmscan-remove-unused-mm_vmscan_memcg_isolate.patch
mm-vmscan-add-active-list-aging-tracepoint.patch
mm-vmscan-add-active-list-aging-tracepoint-update.patch
mm-vmscan-show-the-number-of-skipped-pages-in-mm_vmscan_lru_isolate.patch
mm-vmscan-show-lru-name-in-mm_vmscan_lru_isolate-tracepoint.patch
mm-vmscan-extract-shrink_page_list-reclaim-counters-into-a-struct.patch
mm-vmscan-enhance-mm_vmscan_lru_shrink_inactive-tracepoint.patch
mm-vmscan-add-mm_vmscan_inactive_list_is_low-tracepoint.patch
trace-vmscan-postprocess-sync-with-tracepoints-updates.patch
mm-vmscan-do-not-count-freed-pages-as-pgdeactivate.patch
mm-vmscan-cleanup-lru-size-claculations.patch
mm-vmscan-consider-eligible-zones-in-get_scan_count.patch
revert-mm-bail-out-in-shrink_inactive_list.patch
mm-page_alloc-do-not-report-all-nodes-in-show_mem.patch
mm-page_alloc-warn_alloc-print-nodemask.patch
arch-mm-remove-arch-specific-show_mem.patch
lib-show_memc-teach-show_mem-to-work-with-the-given-nodemask.patch
mm-consolidate-gfp_nofail-checks-in-the-allocator-slowpath.patch
mm-oom-do-not-enfore-oom-killer-for-__gfp_nofail-automatically.patch
mm-help-__gfp_nofail-allocations-which-do-not-trigger-oom-killer.patch
mm-page_alloc-drain-per-cpu-pages-from-workqueue-context-fix.patch
mm-page_alloc-use-static-global-work_struct-for-draining-per-cpu-pages-fix.patch
userfaultfd-non-cooperative-add-event-for-memory-unmaps-fix.patch
vmalloc-back-of-when-the-current-is-killed.patch

--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Kernel Archive]     [IETF Annouce]     [DCCP]     [Netdev]     [Networking]     [Security]     [Bugtraq]     [Yosemite]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux SCSI]

  Powered by Linux