linux-kernel - Re: WARNING in _

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Message-ID: <fc4cf42d-ea06-f405-b3ff-0579cf67e4ec@redhat.com>
Date:   Tue, 30 Jul 2019 16:03:45 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     syzbot <syzbot+e58112d71f77113ddb7b@...kaller.appspotmail.com>,
        aarcange@...hat.com, akpm@...ux-foundation.org,
        christian@...uner.io, davem@...emloft.net, ebiederm@...ssion.com,
        elena.reshetova@...el.com, guro@...com, hch@...radead.org,
        james.bottomley@...senpartnership.com, jglisse@...hat.com,
        keescook@...omium.org, ldv@...linux.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-parisc@...r.kernel.org,
        luto@...capital.net, mhocko@...e.com, mingo@...nel.org,
        namit@...are.com, peterz@...radead.org,
        syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk,
        wad@...omium.org
Subject: Re: WARNING in __mmdrop


On 2019/7/30 下午3:44, Jason Wang wrote:
>>>
>>> }
>> Looks good but I'd like to think of a strategy/existing lock that let us
>> block properly as opposed to spinning, that would be more friendly to
>> e.g. the realtime patch.
>
>
> Does it make sense to disable preemption in the critical section? Then 
> we don't need to block and we have a deterministic time spent on 
> memory accssors?


Ok, touching preempt counter seems a little bit expensive in the fast 
path. Will try for blocking.

Thanks