2.5.21 - console_unblank.

From: Martin Schwidefsky (martin.schwidefsky@debitel.net)
Date: Mon Jun 10 2002 - 17:32:29 EST

in my s390 bag of patches I have another one... console_unblank can cause
an endless trap loop if the console semaphore is already taken and
console_unblank is called in interrupt context. To avoid the trap loop
just try to take to semaphore with down_trylock and exit if its fails.
Its not perfect since c->unblank() is not called in this case but way
better than an endlessly looping cpu. s390/s390x are the only two
architectures that still use console_unblank and for us this is acceptable.
The second change in this patch is to increase the log buffer to 128K. We
do print a LOT of message if cio_msg=yes is used.

blue skies,

diff -urN linux-2.5.21/kernel/printk.c linux-2.5.21-s390/kernel/printk.c
--- linux-2.5.21/kernel/printk.c Sun Jun 9 07:29:53 2002
+++ linux-2.5.21-s390/kernel/printk.c Tue Apr 30 18:08:43 2002
@@ -31,6 +31,8 @@
 #if defined(CONFIG_MULTIQUAD) || defined(CONFIG_IA64)
 #define LOG_BUF_LEN (65536)
+#elif defined(CONFIG_ARCH_S390)
+#define LOG_BUF_LEN (131072)
 #elif defined(CONFIG_SMP)
 #define LOG_BUF_LEN (32768)
@@ -553,7 +555,14 @@
         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)
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

This archive was generated by hypermail 2b29 : Sat Jun 15 2002 - 22:00:19 EST