From: Robert Love <rml@tech9.net>
To: Robert Love <rml@tech9.net>
Cc: linus@transmeta.com, laughing@shared-source.org,
linux-kernel@vger.kernel.org, tytso@thunk.org,
andrewm@uow.edu.au
Subject: Re: [PATCH] tty race on con_close and con_flush_chars
Date: 29 Oct 2001 22:13:55 -0500 [thread overview]
Message-ID: <1004411636.807.262.camel@phantasy> (raw)
In-Reply-To: <1004403868.809.147.camel@phantasy>
In-Reply-To: <1004403868.809.147.camel@phantasy>
Someone pointed out (via private email) that a race can still exist
between checking that vt is non-zero and acquiring the semaphore,
especially since we can sleep doing that.
I agree; the following patch should alleviate that race.
diff -u linux-2.4.13-ac5/drivers/char/console.c
linux/drivers/char/console.c
--- linux-2.4.13-ac5/drivers/char/console.c Mon Oct 29 17:27:19 2001
+++ linux/drivers/char/console.c Mon Oct 29 22:11:27 2001
@@ -2387,8 +2387,14 @@
return;
pm_access(pm_con);
+
+ /*
+ * If we raced with con_close(), `vt' may be null.
+ * Hence this bandaid. - akpm
+ */
acquire_console_sem();
- set_cursor(vt->vc_num);
+ if (vt)
+ set_cursor(vt->vc_num);
release_console_sem();
}
Robert Love
next prev parent reply other threads:[~2001-10-30 3:13 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-10-30 1:04 [PATCH] tty race on con_close and con_flush_chars Robert Love
2001-10-30 3:13 ` Robert Love [this message]
2001-10-31 5:08 ` Tachino Nobuhiro
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