Messages in this thread Patch in this message | | | From | Arnd Bergmann <> | Subject | [PATCH] 12/18 console_unblank bug fix | Date | Mon, 5 Aug 2002 19:47:55 +0200 |
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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();
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