Re: [PATCH] mm: cond_resched in tlb_flush_mmu to fix soft lockups on !CONFIG_PREEMPT

[Simon Jeons <simon.jeons@gmail.com>]

Hi Michal,
On 12/19/2012 12:11 AM, Michal Hocko wrote:
> Since e303297 (mm: extended batches for generic mmu_gather) we are batching
> pages to be freed until either tlb_next_batch cannot allocate a new batch or we
> are done.

Is there material introduce mmu_gather?

>
> This works just fine most of the time but we can get in troubles with
> non-preemptible kernel (CONFIG_PREEMPT_NONE or CONFIG_PREEMPT_VOLUNTARY) on
> large machines where too aggressive batching might lead to soft lockups during
> process exit path (exit_mmap) because there are no scheduling points down the
> free_pages_and_swap_cache path and so the freeing can take long enough to
> trigger the soft lockup.
>
> The lockup is harmless except when the system is setup to panic on
> softlockup which is not that unusual.
>
> The simplest way to work around this issue is to explicitly cond_resched per
> batch in tlb_flush_mmu (1020 pages on x86_64).
>
> The following lockup has been reported for 3.0 kernel with a huge process
> (in order of hundreds gigs but I do know any more details).
>
> [65674.040540] BUG: soft lockup - CPU#56 stuck for 22s! [kernel:31053]
> [65674.040544] Modules linked in: af_packet nfs lockd fscache auth_rpcgss nfs_acl sunrpc mptctl mptbase autofs4 binfmt_misc dm_round_robin dm_multipath bonding cpufreq_conservative cpufreq_userspace cpufreq_powersave pcc_cpufreq mperf microcode fuse loop osst sg sd_mod crc_t10dif st qla2xxx scsi_transport_fc scsi_tgt netxen_nic i7core_edac iTCO_wdt joydev e1000e serio_raw pcspkr edac_core iTCO_vendor_support acpi_power_meter rtc_cmos hpwdt hpilo button container usbhid hid dm_mirror dm_region_hash dm_log linear uhci_hcd ehci_hcd usbcore usb_common scsi_dh_emc scsi_dh_alua scsi_dh_hp_sw scsi_dh_rdac scsi_dh dm_snapshot pcnet32 mii edd dm_mod raid1 ext3 mbcache jbd fan thermal processor thermal_sys hwmon cciss scsi_mod
> [65674.040602] Supported: Yes
> [65674.040604] CPU 56
> [65674.040639] Pid: 31053, comm: kernel Not tainted 3.0.31-0.9-default #1 HP ProLiant DL580 G7
> [65674.040643] RIP: 0010:[<ffffffff81443a88>]  [<ffffffff81443a88>] _raw_spin_unlock_irqrestore+0x8/0x10
> [65674.040656] RSP: 0018:ffff883ec1037af0  EFLAGS: 00000206
> [65674.040657] RAX: 0000000000000e00 RBX: ffffea01a0817e28 RCX: ffff88803ffd9e80
> [65674.040659] RDX: 0000000000000200 RSI: 0000000000000206 RDI: 0000000000000206
> [65674.040661] RBP: 0000000000000002 R08: 0000000000000001 R09: ffff887ec724a400
> [65674.040663] R10: 0000000000000000 R11: dead000000200200 R12: ffffffff8144c26e
> [65674.040665] R13: 0000000000000030 R14: 0000000000000297 R15: 000000000000000e
> [65674.040667] FS:  00007ed834282700(0000) GS:ffff88c03f200000(0000) knlGS:0000000000000000
> [65674.040669] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [65674.040671] CR2: 000000000068b240 CR3: 0000003ec13c5000 CR4: 00000000000006e0
> [65674.040673] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [65674.040675] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [65674.040678] Process kernel (pid: 31053, threadinfo ffff883ec1036000, task ffff883ebd5d4100)
> [65674.040680] Stack:
> [65674.042972]  ffffffff810fc935 ffff88a9f1e182b0 0000000000000206 0000000000000009
> [65674.042978]  0000000000000000 ffffea01a0817e60 ffffea0211d3a808 ffffea0211d3a840
> [65674.042983]  ffffea01a0827a28 ffffea01a0827a60 ffffea0288a598c0 ffffea0288a598f8
> [65674.042989] Call Trace:
> [65674.045765]  [<ffffffff810fc935>] release_pages+0xc5/0x260
> [65674.045779]  [<ffffffff811289dd>] free_pages_and_swap_cache+0x9d/0xc0
> [65674.045786]  [<ffffffff81115d6c>] tlb_flush_mmu+0x5c/0x80
> [65674.045791]  [<ffffffff8111628e>] tlb_finish_mmu+0xe/0x50
> [65674.045796]  [<ffffffff8111c65d>] exit_mmap+0xbd/0x120
> [65674.045805]  [<ffffffff810582d9>] mmput+0x49/0x120
> [65674.045813]  [<ffffffff8105cbb2>] exit_mm+0x122/0x160
> [65674.045818]  [<ffffffff8105e95a>] do_exit+0x17a/0x430
> [65674.045824]  [<ffffffff8105ec4d>] do_group_exit+0x3d/0xb0
> [65674.045831]  [<ffffffff8106f7c7>] get_signal_to_deliver+0x247/0x480
> [65674.045840]  [<ffffffff81002931>] do_signal+0x71/0x1b0
> [65674.045845]  [<ffffffff81002b08>] do_notify_resume+0x98/0xb0
> [65674.045853]  [<ffffffff8144bb60>] int_signal+0x12/0x17
> [65674.046737] DWARF2 unwinder stuck at int_signal+0x12/0x17
>
> Signed-off-by: Michal Hocko <mhocko@suse.cz>
> Cc: stable@vger.kernel.org # 3.0 and higher
> ---
>   mm/memory.c |    1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 1f6cae4..bcd3d5c 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -239,6 +239,7 @@ void tlb_flush_mmu(struct mmu_gather *tlb)
>   	for (batch = &tlb->local; batch; batch = batch->next) {
>   		free_pages_and_swap_cache(batch->pages, batch->nr);
>   		batch->nr = 0;
> +		cond_resched();
>   	}
>   	tlb->active = &tlb->local;
>   }

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