On 03/20/2013 03:55 PM, Rik van Riel wrote:
> This series makes the sysv semaphore code more scalable,
> by reducing the time the semaphore lock is held, and making
> the locking more scalable for semaphore arrays with multiple
> semaphores.
Hi Rik,
Another issue that came up is:
[ 96.347341] ================================================
[ 96.348085] [ BUG: lock held when returning to user space! ]
[ 96.348834] 3.9.0-rc4-next-20130326-sasha-00011-gbcb2313 #318 Tainted: G
W
[ 96.360300] ------------------------------------------------
[ 96.361084] trinity-child9/7583 is leaving the kernel with locks still held!
[ 96.362019] 1 lock held by trinity-child9/7583:
[ 96.362610] #0: (rcu_read_lock){.+.+..}, at: [<ffffffff8192eafb>]
SYSC_semtimedop+0x1fb/0xec0
It seems that we can leave semtimedop without releasing the rcu read lock.
I'm a bit confused by what's going on in semtimedop with regards to rcu read
lock, it
seems that this behaviour is actually intentional?
rcu_read_lock();
sma = sem_obtain_object_check(ns, semid);
if (IS_ERR(sma)) {
if (un)
rcu_read_unlock();
error = PTR_ERR(sma);
goto out_free;
}
When I've looked at that it seems that not releasing the read lock was (very)
intentional.
After that, the only code path that would release the lock starts with:
if (un) {
...
So we won't release the lock at all if un is NULL?
Thanks,
Sasha
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