Hello Oleg, On Mon, Dec 2, 2013 at 4:24 PM, Oleg Nesterov <o...@redhat.com> wrote: > This was reported several times, I believe the first report is > http://marc.info/?l=linux-kernel&m=127688978121665. Hmm, 3 years > ago. The lockless while_each_thread() is racy and broken, almost > every user can loop forever. > > Recently people started to report they actually hit this problem in > oom_kill.c. This doesn't really matter and I can be wrong, but in > fact I do not think they really hit this race, it is very unlikely. > Another problem with while_each_thread() is that it is very easy > to use it wrongly, and oom_kill.c is the good example. > > I came to conclusion that it is practically impossible to send a > single series which fixes all problems, too many different users. > > So 1/2 adds the new for_each_thread() interface, and 2/2 fixes oom > kill as an example. > > We obviously need a lot more changes like 2/2 before we can kill > while_each_thread() and task_struct->thread_group, but I hope they > will be straighforward. And in fact I hope that task->thread_group > can go away before we change all users of while_each_thread(). > > David, et al, I din't actually test 2/2, I do not know how. Please > review, although it looks simple.
I was wondering if this patch was also targeted for stable branch? Before this patch, I was testing this one https://lkml.org/lkml/2013/11/13/336 which is fixing my oom issues. I applied the two patches on top of a 3.10.x and got some tasks stalled after the first OOM: php5-fpm invoked oom-killer: gfp_mask=0xd0, order=0, oom_score_adj=0 php5-fpm cpuset=VM_X mems_allowed=0-1 CPU: 21 PID: 28256 Comm: php5-fpm Not tainted 3.10.22 #1 Hardware name: Dell Inc. PowerEdge C8220/0TDN55, BIOS 1.1.17 01/09/2013 ffffc9001e3c9000 ffff881fbacbfbe8 ffffffff81569220 ffff881fbacbfc88 ffffffff815662f1 ffff882011bb4800 0000000000020000 ffff881fbacbfc28 ffffffff8156d133 0000000000000206 0000000000000206 ffff881f00000000 Call Trace: [<ffffffff81569220>] dump_stack+0x19/0x21 [<ffffffff815662f1>] dump_header+0x7a/0x26c [<ffffffff8156d133>] ? preempt_schedule+0x33/0x50 [<ffffffff8156e597>] ? _raw_spin_unlock_irqrestore+0x67/0x70 [<ffffffff8124b026>] ? ___ratelimit+0xa6/0x130 [<ffffffff810cb2b0>] oom_kill_process+0x2a0/0x440 [<ffffffff8104e0f0>] ? has_capability+0x20/0x20 [<ffffffff8111c8bd>] mem_cgroup_oom_synchronize+0x59d/0x5c0 [<ffffffff8111bbc0>] ? mem_cgroup_charge_common+0xa0/0xa0 [<ffffffff810cbc03>] pagefault_out_of_memory+0x13/0x90 [<ffffffff81564022>] mm_fault_error+0xb8/0x19b [<ffffffff8102b073>] __do_page_fault+0x543/0x5b0 [<ffffffff8156c6ac>] ? __schedule+0x3dc/0xd90 [<ffffffff8107c970>] ? hrtick_update+0x70/0x70 [<ffffffff8109be27>] ? SyS_futex+0x97/0x2f0 [<ffffffff8156f21a>] ? retint_swapgs_pax+0xd/0x12 [<ffffffff81252621>] ? trace_hardirqs_off_thunk+0x3a/0x3c [<ffffffff8102b119>] do_page_fault+0x9/0x20 [<ffffffff8156f4c8>] page_fault+0x38/0x40 Task in /lxc/VM_X killed as a result of limit of /lxc/VM_X memory: usage 254644kB, limit 262144kB, failcnt 38594 memory+swap: usage 524288kB, limit 524288kB, failcnt 803 kmem: usage 0kB, limit 9007199254740991kB, failcnt 0 Memory cgroup stats for /lxc/VM_X: cache:196KB rss:252116KB rss_huge:4096KB mapped_file:164KB swap:274236KB inactive_anon:124788KB active_anon:124332KB inactive_file:0KB active_file:0KB unevictable:0KB [ pid ] uid tgid total_vm rss nr_ptes swapents oom_score_adj name [16017] 0 16017 4444 336 14 94 0 paas-start [18020] 5101 18020 64126 2113 57 4645 -1000 mysqld [19162] 5000 19162 87663 463 122 1396 0 php5-fpm [19216] 5001 19216 24156 473 51 444 0 apache2 [20257] 5001 20257 176880 656 122 2600 0 apache2 [20353] 0 20353 1023 108 8 21 0 sleep [27746] 5000 27746 90454 1025 139 4316 0 php5-fpm [28176] 5000 28176 348410 59568 547 53877 0 php5-fpm INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 21, t=15014 jiffies, g=65569, c=65568, q=6537) INFO: Stall ended before state dump start INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 21, t=60019 jiffies, g=65569, c=65568, q=15632) INFO: Stall ended before state dump start INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 21, t=105024 jiffies, g=65569, c=65568, q=32303) INFO: Stall ended before state dump start INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 21, t=150029 jiffies, g=65569, c=65568, q=43552) INFO: Stall ended before state dump start INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 5, t=195034 jiffies, g=65569, c=65568, q=194557) INFO: Stall ended before state dump start INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 21, t=240039 jiffies, g=65569, c=65568, q=205866) INFO: Stall ended before state dump start INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 21, t=285044 jiffies, g=65569, c=65568, q=238233) INFO: Stall ended before state dump start INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 21, t=330049 jiffies, g=65569, c=65568, q=274925) INFO: Stall ended before state dump start INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 5, t=375054 jiffies, g=65569, c=65568, q=297436) INFO: Stall ended before state dump start -- William -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
