From: Tejun Heo Date: Fri, 24 Jun 2016 21:49:54 +0000 (-0700) Subject: memcg: mem_cgroup_migrate() may be called with irq disabled X-Git-Tag: v4.7-rc5~11^2~12 X-Git-Url: http://git.cascardo.eti.br/?p=cascardo%2Flinux.git;a=commitdiff_plain;h=d93c4130a7d049b234b5d5a15808eaf5406f2789 memcg: mem_cgroup_migrate() may be called with irq disabled mem_cgroup_migrate() uses local_irq_disable/enable() but can be called with irq disabled from migrate_page_copy(). This ends up enabling irq while holding a irq context lock triggering the following lockdep warning. Fix it by using irq_save/restore instead. ================================= [ INFO: inconsistent lock state ] 4.7.0-rc1+ #52 Tainted: G W --------------------------------- inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage. kcompactd0/151 [HC0[0]:SC0[0]:HE1:SE1] takes: (&(&ctx->completion_lock)->rlock){+.?.-.}, at: [<000000000038fd96>] aio_migratepage+0x156/0x1e8 {IN-SOFTIRQ-W} state was registered at: __lock_acquire+0x5b6/0x1930 lock_acquire+0xee/0x270 _raw_spin_lock_irqsave+0x66/0xb0 aio_complete+0x98/0x328 dio_complete+0xe4/0x1e0 blk_update_request+0xd4/0x450 scsi_end_request+0x48/0x1c8 scsi_io_completion+0x272/0x698 blk_done_softirq+0xca/0xe8 __do_softirq+0xc8/0x518 irq_exit+0xee/0x110 do_IRQ+0x6a/0x88 io_int_handler+0x11a/0x25c __mutex_unlock_slowpath+0x144/0x1d8 __mutex_unlock_slowpath+0x140/0x1d8 kernfs_iop_permission+0x64/0x80 __inode_permission+0x9e/0xf0 link_path_walk+0x6e/0x510 path_lookupat+0xc4/0x1a8 filename_lookup+0x9c/0x160 user_path_at_empty+0x5c/0x70 SyS_readlinkat+0x68/0x140 system_call+0xd6/0x270 irq event stamp: 971410 hardirqs last enabled at (971409): migrate_page_move_mapping+0x3ea/0x588 hardirqs last disabled at (971410): _raw_spin_lock_irqsave+0x3c/0xb0 softirqs last enabled at (970526): __do_softirq+0x460/0x518 softirqs last disabled at (970519): irq_exit+0xee/0x110 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(&ctx->completion_lock)->rlock); lock(&(&ctx->completion_lock)->rlock); *** DEADLOCK *** 3 locks held by kcompactd0/151: #0: (&(&mapping->private_lock)->rlock){+.+.-.}, at: aio_migratepage+0x42/0x1e8 #1: (&ctx->ring_lock){+.+.+.}, at: aio_migratepage+0x5a/0x1e8 #2: (&(&ctx->completion_lock)->rlock){+.?.-.}, at: aio_migratepage+0x156/0x1e8 stack backtrace: CPU: 20 PID: 151 Comm: kcompactd0 Tainted: G W 4.7.0-rc1+ #52 Call Trace: show_trace+0xea/0xf0 show_stack+0x72/0xf0 dump_stack+0x9a/0xd8 print_usage_bug.part.27+0x2d4/0x2e8 mark_lock+0x17e/0x758 mark_held_locks+0xa2/0xd0 trace_hardirqs_on_caller+0x140/0x1c0 mem_cgroup_migrate+0x266/0x370 aio_migratepage+0x16a/0x1e8 move_to_new_page+0xb0/0x260 migrate_pages+0x8f4/0x9f0 compact_zone+0x4dc/0xdc8 kcompactd_do_work+0x1aa/0x358 kcompactd+0xba/0x2c8 kthread+0x10a/0x110 kernel_thread_starter+0x6/0xc kernel_thread_starter+0x0/0xc INFO: lockdep is turned off. Link: http://lkml.kernel.org/r/20160620184158.GO3262@mtj.duckdns.org Link: http://lkml.kernel.org/g/5767CFE5.7080904@de.ibm.com Fixes: 74485cf2bc85 ("mm: migrate: consolidate mem_cgroup_migrate() calls") Signed-off-by: Tejun Heo Reported-by: Christian Borntraeger Acked-by: Johannes Weiner Acked-by: Michal Hocko Reviewed-by: Vladimir Davydov Cc: [4.5+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 75e74408cc8f..d4a33e1b77d7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5544,6 +5544,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) struct mem_cgroup *memcg; unsigned int nr_pages; bool compound; + unsigned long flags; VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage); VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); @@ -5574,10 +5575,10 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) commit_charge(newpage, memcg, false); - local_irq_disable(); + local_irq_save(flags); mem_cgroup_charge_statistics(memcg, newpage, compound, nr_pages); memcg_check_events(memcg, newpage); - local_irq_enable(); + local_irq_restore(flags); } DEFINE_STATIC_KEY_FALSE(memcg_sockets_enabled_key);