From: Daniel Phillips <phillips@innominate.de>
To: linux-kernel@vger.kernel.org
Subject: SMP Race in brelse
Date: Fri, 2 Feb 2001 15:19:34 +0100 [thread overview]
Message-ID: <0102021907250D.15914@gimli> (raw)
There is a rare SMP race in brelse:
1138 void __brelse(struct buffer_head * buf)
1139 {
1140 if (atomic_read(&buf->b_count)) {
1141 atomic_dec(&buf->b_count);
1142 return;
1143 }
1144 printk("VFS: brelse: Trying to free free buffer\n");
1145 }
cpu1 cpu2
Starting with buf->b_count = 1, if we have:
if (atomic_read(&buf->b_count))
if (atomic_read(&buf->b_count))
atomic_dec(&buf->b_count);
atomic_dec(&buf->b_count);
buf->b_count is now 0, but it should be -1, we fail to to report
an erroneous extra brelse.
--
Daniel
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next reply other threads:[~2001-02-02 18:09 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-02-02 14:19 Daniel Phillips [this message]
2001-02-02 18:24 ` Tigran Aivazian
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