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From: Michal Hocko <>
To: "Pasi Sjöholm" <>
	"Pasi Sjöholm" <>
Subject: Re: [PATCH] mm/swapfile.c: use spin_lock_bh with swap_lock to avoid deadlocks
Date: Wed, 4 Feb 2015 13:26:48 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Wed 04-02-15 01:48:23, Pasi Sjöholm wrote:
> On 03.02.2015 15:14, Michal Hocko wrote:
> >> It is possible to get kernel in deadlock-state if swap_lock is not locked
> >> with spin_lock_bh by calling si_swapinfo() simultaneously through
> >> timer_function and registered vm shinker callback-function.
> >>
> >> BUG: spinlock recursion on CPU#0, main/2447
> >> lock: swap_lock+0x0/0x10, .magic: dead4ead, .owner: main/2447, .owner_cpu: 0
> >> [<c010b938>] (unwind_backtrace+0x0/0x11c) from [<c03e9be0>] (do_raw_spin_lock+0x48/0x154)
> >> [<c03e9be0>] (do_raw_spin_lock+0x48/0x154) from [<c0226e10>] (si_swapinfo+0x10/0x90)
> >> [<c0226e10>] (si_swapinfo+0x10/0x90) from [<c04d7e18>] (timer_function+0x24/0x258)
> > Who is calling si_swapinfo from timer_function? AFAICS the vanilla
> > kernel doesn't do that. Or am I missing something?
> Nothing in vanilla kernel, but "memnotify"
> ( together with modified
> lowmemorykiller (drivers/staging/android/lowmemorykiller.c) which takes
> in account also the available swap (calling si_swapinfo as well) will
> cause the deadlock.
> Memnotify uses timer (with backoff) for checking the memory pressure
> which can be then used to let the processes itself adjust their memory
> pressure before getting killed by the modified lowmemorykiller.

We are not usually changing the core kernel for an out of tree
functionality. So NAK to this patch.
Michal Hocko

      reply	other threads:[~2015-02-04 12:26 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-02 16:25 pasi.sjoholm
2015-02-03 13:14 ` Michal Hocko
2015-02-03 23:48   ` Pasi Sjöholm
2015-02-04 12:26     ` Michal Hocko [this message]

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