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authorJens Axboe <jens.axboe@oracle.com>2008-05-29 09:35:22 +0200
committerJens Axboe <jens.axboe@oracle.com>2008-07-03 13:21:12 +0200
commit863fddcb4b0caee4c2d5bd6e3b28779920516db3 (patch)
tree9170df5fb0e26d77d45017069b7756f7c80afde5 /block
parent9a11b4ed0e7c44bca7c939aa544c3c47aae40c12 (diff)
as-iosched: properly protect ioc_gone and ioc count
If we have multiple tasks freeing io contexts when as-iosched is being unloaded, we could complete() ioc_gone twice. Fix that by protecting ioc_gone complete() and clearing with a spinlock for just that purpose. Doesn't matter from a performance perspective, since it'll only enter that path when ioc_gone != NULL (when as-iosched is being rmmod'ed). Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block')
-rw-r--r--block/as-iosched.c18
1 files changed, 15 insertions, 3 deletions
diff --git a/block/as-iosched.c b/block/as-iosched.c
index 743f33a01a07..9735acb5b4f5 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -151,6 +151,7 @@ enum arq_state {
static DEFINE_PER_CPU(unsigned long, ioc_count);
static struct completion *ioc_gone;
+static DEFINE_SPINLOCK(ioc_gone_lock);
static void as_move_to_dispatch(struct as_data *ad, struct request *rq);
static void as_antic_stop(struct as_data *ad);
@@ -164,8 +165,19 @@ static void free_as_io_context(struct as_io_context *aic)
{
kfree(aic);
elv_ioc_count_dec(ioc_count);
- if (ioc_gone && !elv_ioc_count_read(ioc_count))
- complete(ioc_gone);
+ if (ioc_gone) {
+ /*
+ * AS scheduler is exiting, grab exit lock and check
+ * the pending io context count. If it hits zero,
+ * complete ioc_gone and set it back to NULL.
+ */
+ spin_lock(&ioc_gone_lock);
+ if (ioc_gone && !elv_ioc_count_read(ioc_count)) {
+ complete(ioc_gone);
+ ioc_gone = NULL;
+ }
+ spin_unlock(&ioc_gone_lock);
+ }
}
static void as_trim(struct io_context *ioc)
@@ -1493,7 +1505,7 @@ static void __exit as_exit(void)
/* ioc_gone's update must be visible before reading ioc_count */
smp_wmb();
if (elv_ioc_count_read(ioc_count))
- wait_for_completion(ioc_gone);
+ wait_for_completion(&all_gone);
synchronize_rcu();
}

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