Messages in this thread | | | Date | Fri, 22 Mar 2013 16:01:05 -0700 | Subject | Re: [PATCH 7/7] ipc,sem: fine grained locking for semtimedop | From | Michel Lespinasse <> |
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Sorry for the late reply; I've been swamped and am behind on my upstream mail.
On Wed, Mar 20, 2013 at 12:55 PM, Rik van Riel <riel@surriel.com> wrote: > +static inline int sem_lock(struct sem_array *sma, struct sembuf *sops, > + int nsops) > +{ > + int locknum; > + if (nsops == 1 && !sma->complex_count) { > + struct sem *sem = sma->sem_base + sops->sem_num; > + > + /* Lock just the semaphore we are interested in. */ > + spin_lock(&sem->lock); > + > + /* > + * If sma->complex_count was set while we were spinning, > + * we may need to look at things we did not lock here. > + */ > + if (unlikely(sma->complex_count)) { > + spin_unlock(&sma->sem_perm.lock);
I believe this should be spin_unlock(&sem->lock) instead ?
> + goto lock_all; > + } > + locknum = sops->sem_num; > + } else { > + int i; > + /* Lock the sem_array, and all the semaphore locks */ > + lock_all: > + spin_lock(&sma->sem_perm.lock); > + for (i = 0; i < sma->sem_nsems; i++) {
Do we have to lock every sem from the array instead of just the ones that are being operated on in sops ? (I'm not sure either way, as I don't fully understand the queueing of complex ops)
If we want to keep the loop as is, then we may at least remove the sops argument to sem_lock() since we only care about nsops.
> + struct sem *sem = sma->sem_base + i; > + spin_lock(&sem->lock); > + } > + locknum = -1; > + } > + return locknum; > +}
That's all I have. Very nice test results BTW!
Reviewed-by: Michel Lespinasse <walken@google.com>
-- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies.
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