Messages in this thread | | | Date | Thu, 20 Jan 2005 12:44:05 +1100 | From | Nick Piggin <> | Subject | Re: [RFC][PATCH 2/4] interruptible rwsem operations (i386, core) |
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David Howells wrote: > Dominik Brodowski <linux@dominikbrodowski.de> wrote: > > >>Add functions down_read_interruptible, and down_write_interruptible to rw >>semaphores. Implement these for i386. >>... > > >>+static inline int >>+rwsem_down_interruptible_failed_common(struct rw_semaphore *sem, >>+ struct rwsem_waiter *waiter, signed long adjustment) >>+{ >>... > > > I wonder if you should check to see if there are any readers that can be woken > up if a sleeping writer is interrupted, but I can't think of a simple way to > do it. > >
I think it will, won't it?
>>-struct rw_semaphore fastcall __sched * >>-rwsem_down_read_failed(struct rw_semaphore *sem) >>+void fastcall __sched rwsem_down_read_failed(struct rw_semaphore *sem) > > > Please don't. > > >>@@ -199,14 +253,33 @@ rwsem_down_read_failed(struct rw_semapho >> RWSEM_WAITING_BIAS - RWSEM_ACTIVE_BIAS); >> >> rwsemtrace(sem, "Leaving rwsem_down_read_failed"); >>- return sem; > > > Ditto. > > >>-struct rw_semaphore fastcall __sched * >>-rwsem_down_write_failed(struct rw_semaphore *sem) >>+void fastcall __sched rwsem_down_write_failed(struct rw_semaphore *sem) > > > Ditto. > > >>@@ -216,10 +289,31 @@ rwsem_down_write_failed(struct rw_semaph >> rwsem_down_failed_common(sem, &waiter, -RWSEM_ACTIVE_BIAS); >> >> rwsemtrace(sem, "Leaving rwsem_down_write_failed"); >>- return sem; > > > Ditto. > > >>@@ -99,11 +103,12 @@ static inline void __down_read(struct rw >> { >> __asm__ __volatile__( >> "# beginning down_read\n\t" >>-LOCK_PREFIX " incl (%%eax)\n\t" /* adds 0x00000001, returns the old value */ >>+LOCK_PREFIX " incl %0\n\t" /* adds 0x00000001, returns the old value */ > > > Ditto. > > >> " js 2f\n\t" /* jump if we weren't granted the lock */ >> "1:\n\t" >> LOCK_SECTION_START("") >> "2:\n\t" >>+ " movl %2,%%eax\n\t" > > > Splat. > > >> " pushl %%ecx\n\t" >> " pushl %%edx\n\t" >> " call rwsem_down_read_failed\n\t" > > > Splat. > > >>@@ -113,11 +118,41 @@ LOCK_PREFIX " incl (%%eax)\n\t" /* >> LOCK_SECTION_END >> "# ending down_read\n\t" >> : "=m"(sem->count) >>- : "a"(sem), "m"(sem->count) >>+ : "m"(sem->count), "m"(sem) >> : "memory", "cc"); >> } > > > You appear to be corrupting EAX. > > >>+static inline int __down_read_interruptible(struct rw_semaphore *sem) > > > Will corrupt EAX. >
I'll fix these up. You're right by the looks.
> >> "# beginning down_write\n\t" >>-LOCK_PREFIX " xadd %%edx,(%%eax)\n\t" /* subtract 0x0000ffff, returns the old value */ >>+LOCK_PREFIX " xadd %%edx,%0\n\t" /* subtract 0x0000ffff, returns the old value */ > > > Again, please don't. It's a lot more readable when it mentions EAX directly, > plus it's also independent of constraint reordering. >
OK I suppose so...
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