From: Arnd Bergmann <arndb@de.ibm.com>
To: Marcelo Tosatti <marcelo@conectiva.com.br>
Cc: lkml <linux-kernel@vger.kernel.org>
Subject: [PATCH] 12/18 console_unblank bug fix
Date: Mon, 5 Aug 2002 19:47:55 +0200 [thread overview]
Message-ID: <200208051947.55433.arndb@de.ibm.com> (raw)
In-Reply-To: <200208051830.50713.arndb@de.ibm.com>
Problem: console_unblank can cause an endless trap loop if the console
semaphore is already taken and console_unblank is called in
interrupt context.
Solution: To avoid the trap loop just try to take the console semaphore
with down_trylock and exit if it fails. It is not perfect
since c->unblank() is not called in this case but way better
than an endless trap loop. s390/s390x are the only two
architectures that still use console_unblank. This patch
has been accepted to 2.5.
diff -urN linux-2.4.19-rc3/kernel/printk.c linux-2.4.19-s390/kernel/printk.c
--- linux-2.4.19-rc3/kernel/printk.c Tue Jul 30 09:02:32 2002
+++ linux-2.4.19-s390/kernel/printk.c Tue Jul 30 09:02:57 2002
@@ -556,7 +556,14 @@
{
struct console *c;
- acquire_console_sem();
+ /*
+ * Try to get the console semaphore. If someone else owns it
+ * we have to return without unblanking because console_unblank
+ * may be called in interrupt context.
+ */
+ if (down_trylock(&console_sem) != 0)
+ return;
+ console_may_schedule = 0;
for (c = console_drivers; c != NULL; c = c->next)
if ((c->flags & CON_ENABLED) && c->unblank)
c->unblank();
next prev parent reply other threads:[~2002-08-05 16:09 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-08-05 18:12 0/18 2.4.19 architecture updates for s390 following Arnd Bergmann
2002-08-05 17:47 ` Arnd Bergmann [this message]
2002-08-05 17:48 ` [PATCH] 13/18 Export elevator_init Arnd Bergmann
2002-08-05 17:50 ` [PATCH] 14/18 support for partition labels in devfs Arnd Bergmann
2002-08-05 17:14 ` Christoph Hellwig
2002-08-05 17:54 ` [PATCH] 15/18 better pte invalidation Arnd Bergmann
2002-08-05 17:01 ` Christoph Hellwig
2002-08-06 11:05 ` Arnd Bergmann
2002-08-06 9:43 ` Christoph Hellwig
2002-08-10 12:28 ` Paul Mackerras
2002-08-05 17:56 ` [PATCH] 16/18 add more possible root devices Arnd Bergmann
2002-08-05 17:15 ` Christoph Hellwig
2002-08-06 11:23 ` Arnd Bergmann
2002-08-05 18:04 ` [PATCH] 17/18 support arbitrary devfs names for tty devices Arnd Bergmann
2002-08-05 18:08 ` [PATCH] 18/18 scsi core changes Arnd Bergmann
2002-08-05 17:12 ` Christoph Hellwig
2002-08-06 11:06 ` Arnd Bergmann
2002-08-06 9:18 ` Christoph Hellwig
2002-08-06 23:10 ` Ingo Adlung
2002-08-06 23:12 ` Christoph Hellwig
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