Code is from linux-mips.org's git tree at 2.6.18 plus some patches from 2.6.18.7. I've run into a deadlock that occurs with the following config: CONFIG_SMP CONFIG_PREEMPT An individual call to __raw_read_trylock() will just return failure if there is already a reader. Any code that tries to take a read lock by looping around __raw_read_trylock() can deadlock if there is already a reader and the lock in question has a mix of irq and non-irq readers. This is the case in the _read_lock() from BUILD_LOCK_OPS() in kernel/spinlock.c. Perhaps someone can confirm this bug by a code inspection, but I think the below patch will fix the issue. Patch should apply ok to 2.6.18.7 (and a similar one to >= 2.6.19) -- Dave Johnson Starent Networks ======================== PATCH FOLLOWS ======================== Fix __raw_read_trylock() to allow multiple readers. A deadlock can occur for mixed irq and non-irq rwlock readers if a 2nd reader attempts to take lock by looping around __raw_read_trylock(). Signed-off-by: Dave Johnson <djohnson+linux-mips@xxxxxxxxxxxxxxxxxxxxxx> --- old/include/asm-mips/spinlock.h 2007-03-05 20:34:51.000000000 -0500 +++ new/include/asm-mips/spinlock.h 2007-03-05 20:35:18.000000000 -0500 @@ -249,7 +249,7 @@ " .set noreorder # __raw_read_trylock \n" " li %2, 0 \n" "1: ll %1, %3 \n" - " bnez %1, 2f \n" + " bltz %1, 2f \n" " addu %1, 1 \n" " sc %1, %0 \n" " beqzl %1, 1b \n" @@ -267,7 +267,7 @@ " .set noreorder # __raw_read_trylock \n" " li %2, 0 \n" "1: ll %1, %3 \n" - " bnez %1, 2f \n" + " bltz %1, 2f \n" " addu %1, 1 \n" " sc %1, %0 \n" " beqz %1, 1b \n"
