linux-kernel - Re: [PATCH] zsmalloc: do not use bit_spin

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Message-ID: <20210114161707.wfgbxi2rppoobfo7@linutronix.de>
Date:   Thu, 14 Jan 2021 17:17:07 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Vitaly Wool <vitaly.wool@...sulko.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Mike Galbraith <efault@....de>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Minchan Kim <minchan@...nel.org>,
        NitinGupta <ngupta@...are.org>
Subject: Re: [PATCH] zsmalloc: do not use bit_spin_lock

On 2020-12-20 08:21:37 [+0100], Vitaly Wool wrote:
> Not really because bit spinlock leaves preemption disabled.

It leaves it disabled for a reason. Now you just spin until the original
context gets back on the CPU. On UP with preemption, if the "lock owner"
gets preempted, the next lock attempt will lock-up the system.

Sebastian