I have a question about "printk: set may_schedule for some of console_trylock() callers" in linux-next.git. I'm trying to dump information of all threads which might be relevant to stalling inside memory allocator. But it seems to me that since this patch changed to allow calling cond_resched() from printk() if it is safe to do so, it is now possible that the thread which invoked the OOM killer can sleep for minutes with the oom_lock mutex held when my dump is in progress. I want to release oom_lock mutex as soon as possible so that other threads can call out_of_memory() to get TIF_MEMDIE and exit their allocations. So, how can I prevent printk() triggered by out_of_memory() from sleeping for minutes with oom_lock mutex held? Guard it with preempt_disable() / preempt_enable() ? Guard it with rcu_read_lock() / rcu_read_unlock() ? ---------- [ 460.893958] tgid=11161 invoked oom-killer: gfp_mask=0x24201ca(GFP_HIGHUSER_MOVABLE|__GFP_COLD), order=0, oom_score_adj=1000 [ 463.892897] tgid=11161 cpuset=/ mems_allowed=0 [ 463.894724] CPU: 1 PID: 12346 Comm: tgid=11161 Not tainted 4.5.0-rc6-next-20160302+ #318 [ 463.897026] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/31/2013 [ 463.899841] 0000000000000286 00000000733ef955 ffff8800778a79b0 ffffffff813a2ded [ 463.902164] 0000000000000000 ffff8800778a7be0 ffff8800778a7a50 ffffffff811c24d0 [ 463.904474] 0000000000000206 ffffffff81810c30 ffff8800778a79f0 ffffffff810bf839 [ 463.906801] Call Trace: [ 463.908101] [<ffffffff813a2ded>] dump_stack+0x85/0xc8 [ 463.909921] [<ffffffff811c24d0>] dump_header+0x5b/0x3b0 [ 463.911759] [<ffffffff810bf839>] ? trace_hardirqs_on_caller+0xf9/0x1c0 [ 463.913833] [<ffffffff810bf90d>] ? trace_hardirqs_on+0xd/0x10 [ 463.915751] [<ffffffff81146f2d>] oom_kill_process+0x37d/0x570 [ 463.918024] [<ffffffff81147366>] out_of_memory+0x1f6/0x5a0 [ 463.919890] [<ffffffff81147424>] ? out_of_memory+0x2b4/0x5a0 [ 463.921784] [<ffffffff8114d041>] __alloc_pages_nodemask+0xc91/0xeb0 [ 463.923788] [<ffffffff81196726>] alloc_pages_current+0x96/0x1b0 [ 463.925729] [<ffffffff8114188d>] __page_cache_alloc+0x12d/0x160 [ 463.927682] [<ffffffff8114537a>] filemap_fault+0x48a/0x6a0 [ 463.929547] [<ffffffff81145247>] ? filemap_fault+0x357/0x6a0 [ 463.931409] [<ffffffff812b9e09>] xfs_filemap_fault+0x39/0x60 [ 463.933255] [<ffffffff8116f19d>] __do_fault+0x6d/0x150 [ 463.934974] [<ffffffff81175b1d>] handle_mm_fault+0xecd/0x1800 [ 463.936791] [<ffffffff81174ca3>] ? handle_mm_fault+0x53/0x1800 [ 463.938617] [<ffffffff8105a796>] __do_page_fault+0x1e6/0x520 [ 463.940380] [<ffffffff8105ab00>] do_page_fault+0x30/0x80 [ 463.942074] [<ffffffff817113e8>] page_fault+0x28/0x30 [ 463.943750] Mem-Info: (...snipped...) [ 554.754959] MemAlloc: tgid=11161(12346) flags=0x400040 switches=865 seq=169 gfp=0x24201ca(GFP_HIGHUSER_MOVABLE|__GFP_COLD) order=0 delay=81602 [ 554.754962] tgid=11161 R running task 0 12346 11056 0x00000080 [ 554.754965] ffff8800778a7838 ffff880034510000 ffff8800778b0000 ffff8800778a8000 [ 554.754966] 0000000000000091 ffffffff82a86fbc 0000000000000004 0000000000000000 [ 554.754967] ffff8800778a7850 ffffffff8170a5dd 0000000000000296 ffff8800778a7860 [ 554.754968] Call Trace: [ 554.754974] [<ffffffff8170a5dd>] preempt_schedule_common+0x1f/0x42 [ 554.754975] [<ffffffff8170a617>] _cond_resched+0x17/0x20 [ 554.754978] [<ffffffff810d17b9>] console_unlock+0x509/0x5c0 [ 554.754979] [<ffffffff810d1b93>] vprintk_emit+0x323/0x540 [ 554.754981] [<ffffffff810d1f0a>] vprintk_default+0x1a/0x20 [ 554.754983] [<ffffffff8114069e>] printk+0x58/0x6f [ 554.754986] [<ffffffff813aaede>] show_mem+0x1e/0xe0 [ 554.754988] [<ffffffff811c24ec>] dump_header+0x77/0x3b0 [ 554.754990] [<ffffffff810bf839>] ? trace_hardirqs_on_caller+0xf9/0x1c0 [ 554.754991] [<ffffffff810bf90d>] ? trace_hardirqs_on+0xd/0x10 [ 554.754993] [<ffffffff81146f2d>] oom_kill_process+0x37d/0x570 [ 554.754995] [<ffffffff81147366>] out_of_memory+0x1f6/0x5a0 [ 554.754996] [<ffffffff81147424>] ? out_of_memory+0x2b4/0x5a0 [ 554.754997] [<ffffffff8114d041>] __alloc_pages_nodemask+0xc91/0xeb0 [ 554.755000] [<ffffffff81196726>] alloc_pages_current+0x96/0x1b0 [ 554.755001] [<ffffffff8114188d>] __page_cache_alloc+0x12d/0x160 [ 554.755003] [<ffffffff8114537a>] filemap_fault+0x48a/0x6a0 [ 554.755004] [<ffffffff81145247>] ? filemap_fault+0x357/0x6a0 [ 554.755006] [<ffffffff812b9e09>] xfs_filemap_fault+0x39/0x60 [ 554.755007] [<ffffffff8116f19d>] __do_fault+0x6d/0x150 [ 554.755009] [<ffffffff81175b1d>] handle_mm_fault+0xecd/0x1800 [ 554.755010] [<ffffffff81174ca3>] ? handle_mm_fault+0x53/0x1800 [ 554.755012] [<ffffffff8105a796>] __do_page_fault+0x1e6/0x520 [ 554.755013] [<ffffffff8105ab00>] do_page_fault+0x30/0x80 [ 554.755015] [<ffffffff817113e8>] page_fault+0x28/0x30 ---------- CONFIG_PREEMPT_NONE=y # CONFIG_PREEMPT_VOLUNTARY is not set # CONFIG_PREEMPT is not set CONFIG_PREEMPT_COUNT=y -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>