Messages in this thread Patch in this message | | | Subject | PATCH: Minimal fix for sysrq on serial console hang | From | Alan Cox <> | Date | Wed, 12 Jul 2006 14:54:21 +0100 |
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When I originally did this change I used oops_in_progress as a locking guide. However it turns out there is one other place that turns all the locking on its head and that is sysrq.
The fix below is a minimal fix to avoid this hanging and worst case may lead to the very rare stuck character as it did pre 2.6.16 anyway but only when using sysrq [which right now hangs the box]
The right fix is probably to unlock on the sysrq path and relock and reconfigure the uart but thats more complex and not low risk at this point in time although I will revisit it after (or during KS/OLS) depending on rmk's view.
Signed-off-by: Alan Cox <alan@redhat.com>
diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.18-rc1/drivers/serial/8250.c linux-2.6.18-rc1/drivers/serial/8250.c --- linux.vanilla-2.6.18-rc1/drivers/serial/8250.c 2006-07-12 12:16:47.000000000 +0100 +++ linux-2.6.18-rc1/drivers/serial/8250.c 2006-07-12 12:21:10.000000000 +0100 @@ -2240,10 +2240,12 @@ touch_nmi_watchdog(); - if (oops_in_progress) { - locked = spin_trylock_irqsave(&up->port.lock, flags); - } else - spin_lock_irqsave(&up->port.lock, flags); + /* + * This can occur during an oops, in which case we want to + * do our best, or sysrq which is hairier and eventually needs + * a nicer solution + */ + locked = spin_trylock_irqsave(&up->port.lock, flags); /* * First save the IER then disable the interrupts - 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/
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