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SubjectRe: [FIX] Make deadlock detection work for file locking
BTW, this is a little off-topic, I kind of wonder what the right semantics
for deadlock detection are with threads. POSIX 1003.1 1996-07-12 says:

"A potential for deadlock occurs if a process controlling a locked
region is put to sleep by attempting to lock the locked region of
another process. If the system detects that sleeping until a
locked region is unlocked would cause a deadlock, the fcntl()
function shall fail with an [EDEADLK] error."

Okay, that's a little vague already. Now let's make it more interesting
by adding threads:

Process Thread Action (executed in this order)
A 1 grab lock X
B 1 grab lock Y
A 2 try to get lock Y
B 2 try to get lock X

Solaris 2.5.1 thinks this is a deadlock. Linux 2.4.0-test1-ac16 thinks
it isn't. I haven't found any definition of what "putting a process to
sleep" means in POSIX.1.

Opinions ?

- Werner

/ Werner Almesberger, ICA, EPFL, CH /
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