On Sat, Apr 25, 2015 at 03:05:15PM +0800, Joseph Qi wrote: > There is a race between purge and get lock resource, which will lead to > ast unfinished and system hung. The case is described below: > > mkdir dlm_thread > ----------------------------------------------------------------------- > o2cb_dlm_lock | > -> dlmlock | > -> dlm_get_lock_resource | > -> __dlm_lookup_lockres_full | > -> spin_unlock(&dlm->spinlock) | > | dlm_run_purge_list > | -> dlm_purge_lockres > | -> dlm_drop_lockres_ref > | -> spin_lock(&dlm->spinlock) > | -> spin_lock(&res->spinlock) > | -> ~DLM_LOCK_RES_DROPPING_REF > | -> spin_unlock(&res->spinlock) > | -> spin_unlock(&dlm->spinlock) > -> spin_lock(&tmpres->spinlock)| > DLM_LOCK_RES_DROPPING_REF cleared | > -> spin_unlock(&tmpres->spinlock) | > return the purged lockres | > > So after this, once ast comes, it will ingore the ast because the > lockres cannot be found anymore. Thus the OCFS2_LOCK_BUSY won't be > cleared and corresponding thread hangs. > The &dlm->spinlock was hold when checking DLM_LOCK_RES_DROPPING_REF at > the very begining. And commit 7b791d6856 (ocfs2/dlm: Fix race during > lockres mastery) moved it up because of the possible wait. > So take the &dlm->spinlock and introduce a new wait function to fix the > race. > > Signed-off-by: Joseph Qi <joseph.qi@xxxxxxxxxx> > Reviewed-by: joyce.xue <xuejiufei@xxxxxxxxxx> > --- > fs/ocfs2/dlm/dlmcommon.h | 2 ++ > fs/ocfs2/dlm/dlmmaster.c | 13 +++++++++---- > fs/ocfs2/dlm/dlmthread.c | 23 +++++++++++++++++++++++ > 3 files changed, 34 insertions(+), 4 deletions(-) <formletter> This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read Documentation/stable_kernel_rules.txt for how to do this properly. </formletter> -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html