Currently, when we enter the wait state due to lack of idle stream, we check idle_strm list without holding the lock in expanding of wait_event define. In this case, some one can see stale value and process could fall into wait state without any upcoming wakeup process. Although I didn't see any error related to this race, it should be fixed.
To fix it, we should check idle_strm with holding the lock and this patch implements it. Signed-off-by: Joonsoo Kim <[email protected]> --- drivers/block/zram/zcomp.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c index 80a62e7..837e9c3 100644 --- a/drivers/block/zram/zcomp.c +++ b/drivers/block/zram/zcomp.c @@ -76,6 +76,17 @@ static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp) return zstrm; } +static bool avail_idle_strm(struct zcomp_strm_multi *zs) +{ + int avail; + + spin_lock(&zs->strm_lock); + avail = !list_empty(&zs->idle_strm); + spin_unlock(&zs->strm_lock); + + return avail; +} + /* * get idle zcomp_strm or wait until other process release * (zcomp_strm_release()) one for us @@ -97,7 +108,7 @@ static struct zcomp_strm *zcomp_strm_multi_find(struct zcomp *comp) /* zstrm streams limit reached, wait for idle stream */ if (zs->avail_strm >= zs->max_strm) { spin_unlock(&zs->strm_lock); - wait_event(zs->strm_wait, !list_empty(&zs->idle_strm)); + wait_event(zs->strm_wait, avail_idle_strm(zs)); continue; } /* allocate new zstrm stream */ @@ -109,7 +120,7 @@ static struct zcomp_strm *zcomp_strm_multi_find(struct zcomp *comp) spin_lock(&zs->strm_lock); zs->avail_strm--; spin_unlock(&zs->strm_lock); - wait_event(zs->strm_wait, !list_empty(&zs->idle_strm)); + wait_event(zs->strm_wait, avail_idle_strm(zs)); continue; } break; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
