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From: Cong Wang <xiyou.wangcong@gmail.com>
To: Leon Romanovsky <leon@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	linux-rdma@vger.kernel.org, Doug Ledford <dledford@redhat.com>,
	Jason Gunthorpe <jgg@mellanox.com>
Subject: Re: [PATCH] infiniband: fix a subtle race condition
Date: Wed, 13 Jun 2018 23:21:54 -0700	[thread overview]
Message-ID: <CAM_iQpXxHk+yFqqK-Hezsc83_mKfbUXr4=jjNnik5DwGscRKUA@mail.gmail.com> (raw)
In-Reply-To: <20180614053446.GB18426@mtr-leonro.mtl.com>

On Wed, Jun 13, 2018 at 10:34 PM, Leon Romanovsky <leon@kernel.org> wrote:
>
> Hi Cong,
>
> If the compiler optimizes the first line (mutex_lock) as you wrote,
> it will reuse "f" for the second line (mutex_unlock) too.

Nope, check the assembly if you don't trust me, at least
my compiler always fetches ctx->file without this patch.

I can show you the assembly code tomorrow (too late to
access my dev machine now).


>
> You need to ensure that ucma_modify_id() doesn't run in parallel to
> anything that uses "ctx->file" directly and indirectly.
>

Talk is easy, show me the code. :) I knew there is probably
some other race with this code even after my patch, possibly with
->close() for example, but for this specific unlock warning, this patch
is sufficient. I can't solve all the races in one patch.

  reply	other threads:[~2018-06-14  6:22 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-13 23:49 [PATCH] infiniband: fix a subtle race condition Cong Wang
2018-06-14  5:34 ` Leon Romanovsky
2018-06-14  6:21   ` Cong Wang [this message]
2018-06-14  7:01     ` Leon Romanovsky
2018-06-14 14:24       ` Jason Gunthorpe
2018-06-14 17:03         ` Cong Wang
2018-06-14 17:24           ` Jason Gunthorpe
2018-06-14 23:14             ` Cong Wang
2018-06-15  2:57               ` Jason Gunthorpe
2018-06-15 17:57                 ` Cong Wang
2018-06-15 19:08                   ` Jason Gunthorpe
2018-06-18 18:40                     ` Cong Wang
2018-06-14 16:57       ` Cong Wang

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