From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Whitehouse Date: Fri, 14 Sep 2007 13:26:42 +0100 Subject: [Cluster-devel] [PATCH] [GFS2] bz 276631 : GFS2: chmod hung - TRY 2 In-Reply-To: <1189742683.5632.13.camel@technetium.msp.redhat.com> References: <1189742683.5632.13.camel@technetium.msp.redhat.com> Message-ID: <1189772802.1068.42.camel@quoit> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hi, Now in the -nmw git tree. Thanks, Steve. On Thu, 2007-09-13 at 23:04 -0500, Bob Peterson wrote: > Josef's right--my bad. Here is the corrected patch for 276631. > > The problem boiled down to a race between the gdlm_init_threads() > function initializing thread1 and its setting of blist = 1. > Essentially, "if (current == ls->thread1)" was checked by the thread > before the thread creator set ls->thread1. > > Since thread1 is the only thread who is allowed to work on the > blocking queue, and since neither thread thought it was thread1, no one > was working on the queue. So everything just sat. > > This patch reuses the ls->async_lock spin_lock to fix the race, > and it fixes the problem. I've done more than 2000 iterations of the > loop that was recreating the failure and it seems to work. > > Dave Teigland brought up the question of whether we should do this > another way. For example, by checking for the task name "lock_dlm1" > instead. I'm open to opinions. > -- > Signed-off-by: Bob Peterson > -- > diff -pur a/fs/gfs2/locking/dlm/thread.c b/fs/gfs2/locking/dlm/thread.c > --- a/fs/gfs2/locking/dlm/thread.c 2007-09-13 17:33:58.000000000 -0500 > +++ b/fs/gfs2/locking/dlm/thread.c 2007-09-13 22:47:14.000000000 -0500 > @@ -279,8 +279,10 @@ static int gdlm_thread(void *data) > /* Only thread1 is allowed to do blocking callbacks since gfs > may wait for a completion callback within a blocking cb. */ > > + spin_lock(&ls->async_lock); > if (current == ls->thread1) > blist = 1; > + spin_unlock(&ls->async_lock); > > while (!kthread_should_stop()) { > set_current_state(TASK_INTERRUPTIBLE); > @@ -338,10 +340,12 @@ int gdlm_init_threads(struct gdlm_ls *ls > struct task_struct *p; > int error; > > + spin_lock(&ls->async_lock); > p = kthread_run(gdlm_thread, ls, "lock_dlm1"); > error = IS_ERR(p); > if (error) { > log_error("can't start lock_dlm1 thread %d", error); > + spin_unlock(&ls->async_lock); > return error; > } > ls->thread1 = p; > @@ -351,9 +355,11 @@ int gdlm_init_threads(struct gdlm_ls *ls > if (error) { > log_error("can't start lock_dlm2 thread %d", error); > kthread_stop(ls->thread1); > + spin_unlock(&ls->async_lock); > return error; > } > ls->thread2 = p; > + spin_unlock(&ls->async_lock); > > return 0; > } > >