linux-kernel - Re: [PATCH 2/6] mm: mark all calls into the vmalloc subsystem as potentially sleeping

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Date:   Wed, 19 Oct 2016 12:15:41 +0100
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     akpm@...ux-foundation.org, joelaf@...gle.com, jszhang@...vell.com,
        joaodias@...gle.com, linux-mm@...ck.org,
        linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] mm: mark all calls into the vmalloc subsystem as
 potentially sleeping

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
[  696.928901]  [<ffffffff8109a943>] finish_task_switch+0x163/0x1e0
[  696.928914]  [<ffffffff8109a845>] ? finish_task_switch+0x65/0x1e0
[  696.928928]  [<ffffffff816125f5>] __schedule+0x1f5/0x7c0
[  696.928940]  [<ffffffff81612c28>] schedule+0x38/0x90
[  696.928953]  [<ffffffff810787b1>] do_wait+0x1d1/0x200
[  696.928966]  [<ffffffff810799b1>] SyS_wait4+0x61/0xc0
[  696.928979]  [<ffffffff81076e50>] ? task_stopped_code+0x50/0x50
[  696.928992]  [<ffffffff81618e6e>] entry_SYSCALL_64_fastpath+0x1c/0xb1

[This was triggered by earlier patch to remove the serialisation and add
cond_resched_lock(&vmap_area_lock)]
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre