On 6/18/09 10:48 AM, "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote: > On Thu, Jun 18, 2009 at 10:39:10AM -0700, Labiaga, Ricardo wrote: >> On 6/18/09 10:31 AM, "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote: >> >>> On Wed, Jun 17, 2009 at 06:50:45PM -0700, Ricardo Labiaga wrote: >>>> renew_client() manipulates the client queue for lease renewal. Need to >>>> obtain the client_mutex before manipulating it. >>>> >>>> Signed-off-by: Ricardo Labiaga <Ricardo.Labiaga@xxxxxxxxxx> >>>> --- >>>> fs/nfsd/nfs4state.c | 2 ++ >>>> 1 files changed, 2 insertions(+), 0 deletions(-) >>>> >>>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c >>>> index 4cb5d1d..18258d7 100644 >>>> --- a/fs/nfsd/nfs4state.c >>>> +++ b/fs/nfsd/nfs4state.c >>>> @@ -1537,7 +1537,9 @@ replay_cache: >>>> * Hold a session reference until done processing the compound: >>>> * nfsd4_put_session called only if the cstate slot is set. >>>> */ >>>> + nfs4_lock_state(); >>>> renew_client(session->se_client); >>>> + nfs4_unlock_state(); >>>> nfsd4_get_session(session); >>>> out: >>>> spin_unlock(&sessionid_lock); >>> >>> We can't take a mutex while handling a spinlock. (And you should have >>> gotten warnings about this--not sure what kernel hacking config options >>> you may need turned on for that.) >>> >> >> Ah, OK. I didn't know that. > > The deadlock: > > Task 1 takes a spinlock. > Task 1 sleeps on the mutex. > Task 2 is scheduled in. > Task 2 requests the same spinlock, spins. > > Now Task 2 is spinning waiting for the spinlock, keeping task 1 from > getting the cpu back and releaseing the spinlock. So, no sleeping under > spinlocks. Right, thanks. - ricardo > >>> Possible hack: add a spinlock that for now will just cover the client >>> lru? >> >> Let me study this some more and see if I can simply drop the sessionid >> spinlock before renewing the state. > > OK. > > --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
