linux-kernel - Re: [PATCH] mm/khugepaged: Fix might_sleep() warn with CONFIG

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Date:   Tue, 29 Oct 2019 14:43:00 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Ville Syrjala <ville.syrjala@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, linux-mm@...ck.org,
        Jérôme Glisse 
        <jglisse@...hat.com>, Ralph Campbell <rcampbell@...dia.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH] mm/khugepaged: Fix might_sleep() warn with
 CONFIG_HIGHPTE=y

On Tue, 29 Oct 2019 23:25:13 +0200 Ville Syrjala <ville.syrjala@...ux.intel.com> wrote:

> From: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> 
> I got some khugepaged spew on a 32bit x86:
> 
> [  217.490026] BUG: sleeping function called from invalid context at include/linux/mmu_notifier.h:346
> [  217.492826] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 25, name: khugepaged
> [  217.495589] INFO: lockdep is turned off.
> [  217.498371] CPU: 1 PID: 25 Comm: khugepaged Not tainted 5.4.0-rc5-elk+ #206
> [  217.501233] Hardware name: System manufacturer P5Q-EM/P5Q-EM, BIOS 2203    07/08/2009
> [  217.501697] Call Trace:
> [  217.501697]  dump_stack+0x66/0x8e
> [  217.501697]  ___might_sleep.cold.96+0x95/0xa6
> [  217.501697]  __might_sleep+0x2e/0x80
> [  217.501697]  collapse_huge_page.isra.51+0x5ac/0x1360
> [  217.501697]  ? __alloc_pages_nodemask+0xec/0xf80
> [  217.501697]  ? __alloc_pages_nodemask+0x191/0xf80
> [  217.501697]  ? trace_hardirqs_on+0x4a/0xf0
> [  217.501697]  khugepaged+0x9a9/0x20f0
> [  217.501697]  ? _raw_spin_unlock+0x21/0x30
> [  217.501697]  ? trace_hardirqs_on+0x4a/0xf0
> [  217.501697]  ? wait_woken+0xa0/0xa0
> [  217.501697]  kthread+0xf5/0x110
> [  217.501697]  ? collapse_pte_mapped_thp+0x3b0/0x3b0
> [  217.501697]  ? kthread_create_worker_on_cpu+0x20/0x20
> [  217.501697]  ret_from_fork+0x2e/0x38
> 
> Looks like it's due to CONFIG_HIGHPTE=y pte_offset_map()->kmap_atomic()
> vs. mmu_notifier_invalidate_range_start(). Let's do the naive approach
> and just reorder the two operations.

Thanks.

I'll add 
Fixes: 810e24e009cf71 ("mm/mmu_notifiers: annotate with might_sleep()")
Cc: <stable@...r.kernel.org>

although 810e24e009cf71 merely exposed the bug.