On 11/08/2016 04:24 PM, Joel Fernandes wrote: > On Wed, Oct 19, 2016 at 4:15 AM, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: >> On Tue, Oct 18, 2016 at 08:56:07AM +0200, Christoph Hellwig wrote: >>> This is how everyone seems to already use them, but let's make that >>> explicit. >> >> Ah, found an exception, vmapped stacks: >> >> [ 696.928541] BUG: sleeping function called from invalid context at mm/vmalloc.c:615 >> [ 696.928576] in_atomic(): 1, irqs_disabled(): 0, pid: 30521, name: bash >> [ 696.928590] 1 lock held by bash/30521: >> [ 696.928600] #0: [ 696.928606] (vmap_area_lock[ 696.928619] ){+.+...}, at: [ 696.928640] [<ffffffff8115f0cf>] __purge_vmap_area_lazy+0x30f/0x370 >> [ 696.928656] CPU: 0 PID: 30521 Comm: bash Tainted: G W 4.9.0-rc1+ #124 >> [ 696.928672] Hardware name: / , BIOS PYBSWCEL.86A.0027.2015.0507.1758 05/07/2015 >> [ 696.928690] ffffc900070f7c70 ffffffff812be1f5 ffff8802750b6680 ffffffff819650a6 >> [ 696.928717] ffffc900070f7c98 ffffffff810a3216 0000000000004001 ffff8802726e16c0 >> [ 696.928743] ffff8802726e19a0 ffffc900070f7d08 ffffffff8115f0f3 ffff8802750b6680 >> [ 696.928768] Call Trace: >> [ 696.928782] [<ffffffff812be1f5>] dump_stack+0x68/0x93 >> [ 696.928796] [<ffffffff810a3216>] ___might_sleep+0x166/0x220 >> [ 696.928809] [<ffffffff8115f0f3>] __purge_vmap_area_lazy+0x333/0x370 >> [ 696.928823] [<ffffffff8115ea68>] ? vunmap_page_range+0x1e8/0x350 >> [ 696.928837] [<ffffffff8115f1b3>] free_vmap_area_noflush+0x83/0x90 >> [ 696.928850] [<ffffffff81160931>] remove_vm_area+0x71/0xb0 >> [ 696.928863] [<ffffffff81160999>] __vunmap+0x29/0xf0 >> [ 696.928875] [<ffffffff81160ab9>] vfree+0x29/0x70 >> [ 696.928888] [<ffffffff81071746>] put_task_stack+0x76/0x120 > > From this traceback, it looks like the lock causing the atomic context > was actually acquired in the vfree path itself, and not by the vmapped > stack user (as it says "vmap_area_lock" held). I am still wondering > why vmap_area_lock was held during the might_sleep(), perhaps you may > not have applied all patches from Chris H? > I don't think that this splat is because we holding vmap_area_lock. Look at cond_resched_lock: #define cond_resched_lock(lock) ({ \ ___might_sleep(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET);\ __cond_resched_lock(lock); \ }) It calls might_sleep() with spin lock still held. AFAIU PREEMPT_LOCK_OFFSET supposed to tell might_sleep() to ignore spin locks and complain iff something else changed preempt_count. -- 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>