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From: Mike Galbraith <efault@gmx.de>
To: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	Barry Song <song.bao.hua@hisilicon.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [patch] zswap: fix zswap_frontswap_load() vs zsmalloc::map/unmap() might_sleep() splat
Date: Sat, 19 Dec 2020 11:59:33 +0100	[thread overview]
Message-ID: <18669bd607ae9efbf4e00e36532c7aa167d0fa12.camel@gmx.de> (raw)
In-Reply-To: <CAM4kBBJZDqZfk+w5Wv4Ye7JythQ-Sr5-==zxeq8M5WCnHpFtEA@mail.gmail.com>

On Sat, 2020-12-19 at 11:46 +0100, Vitaly Wool wrote:
> On Sat, 19 Dec 2020, 11:27 Mike Galbraith, <efault@gmx.de> wrote:
>
> > The kernel that generated that splat was NOT an RT kernel, it was plain
> > master.today with a PREEMPT config.
>
>
> I see, thanks. I don't think it makes things better for zsmalloc
> though. From what I can see, the offending code is this:
>
> >        /* From now on, migration cannot move the object */
> >        pin_tag(handle);
>
> Bit spinlock is taken in pin_tag(). I find the comment above somewhat
> misleading, why is it necessary to take a spinlock to prevent
> migration? I would guess an atomic flag should normally be enough.
>
> zswap is not broken here, it is zsmalloc that needs to be fixed.

Cool, those damn bit spinlocks going away would be a case of happiness
for RT as well :)

	-Mike


  reply	other threads:[~2020-12-19 11:01 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-19 10:04 [patch] zswap: fix zswap_frontswap_load() vs zsmalloc::map/unmap() might_sleep() splat Mike Galbraith
2020-12-19 10:12 ` Mike Galbraith
2020-12-19 10:20   ` Vitaly Wool
2020-12-19 10:27     ` Mike Galbraith
2020-12-19 10:46       ` Vitaly Wool
2020-12-19 10:59         ` Mike Galbraith [this message]
2020-12-19 11:03           ` Mike Galbraith
2020-12-20  0:22           ` [PATCH] zsmalloc: do not use bit_spin_lock Vitaly Wool
2020-12-20  1:18             ` Matthew Wilcox
2020-12-20  7:21               ` Vitaly Wool
2021-01-14 16:17                 ` Sebastian Andrzej Siewior
2020-12-20  1:23             ` Mike Galbraith
2020-12-20  4:11               ` Mike Galbraith
2020-12-20  7:47               ` Mike Galbraith
2020-12-20 21:20                 ` Song Bao Hua (Barry Song)
2020-12-20 22:10                   ` Mike Galbraith
2020-12-20  1:56             ` Mike Galbraith
2020-12-21 17:24             ` Minchan Kim
2020-12-21 19:20               ` Vitaly Wool
2020-12-21 19:50                 ` Shakeel Butt
2020-12-21 20:05                   ` Song Bao Hua (Barry Song)
2020-12-21 21:02                     ` Shakeel Butt
2020-12-21 21:25                       ` Song Bao Hua (Barry Song)
2020-12-21 22:11                         ` Vitaly Wool
2020-12-21 22:42                           ` Song Bao Hua (Barry Song)
2020-12-21 23:35                           ` Song Bao Hua (Barry Song)
2020-12-22  0:59                             ` Vitaly Wool
2020-12-22  1:10                               ` Song Bao Hua (Barry Song)
2020-12-22  1:42                               ` Song Bao Hua (Barry Song)
     [not found]                                 ` <CAM4kBBK=5eBdCjWc5VJXcdr=Z4PV1=ZQ2n8fZmJ6ahJbpUyv2A@mail.gmail.com>
2020-12-22  2:07                                   ` Song Bao Hua (Barry Song)
2020-12-22  2:10                                   ` Song Bao Hua (Barry Song)
2020-12-22  9:44                                     ` Vitaly Wool
2020-12-22 21:06                                       ` Song Bao Hua (Barry Song)
2020-12-23  0:11                                         ` Vitaly Wool
2020-12-23 12:44                                           ` tiantao (H)
2020-12-23 18:25                                             ` Vitaly Wool
2021-01-14 16:18                                               ` Sebastian Andrzej Siewior
2021-01-14 16:29                                                 ` Vitaly Wool
2021-01-14 16:56                                                   ` Sebastian Andrzej Siewior
2021-01-14 17:15                                                     ` Vitaly Wool
2021-01-14 17:18                                                       ` Sebastian Andrzej Siewior
2020-12-21 22:46                         ` Shakeel Butt
2020-12-21 23:02                           ` Song Bao Hua (Barry Song)
2020-12-22  9:20                             ` David Laight
2020-12-21 20:22                 ` Minchan Kim

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