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| author | Jens Axboe <jens.axboe@oracle.com> | 2008-05-29 09:35:22 +0200 |
|---|---|---|
| committer | Jens Axboe <jens.axboe@oracle.com> | 2008-07-03 13:21:12 +0200 |
| commit | 863fddcb4b0caee4c2d5bd6e3b28779920516db3 (patch) | |
| tree | 9170df5fb0e26d77d45017069b7756f7c80afde5 /block | |
| parent | 9a11b4ed0e7c44bca7c939aa544c3c47aae40c12 (diff) | |
| download | linux-863fddcb4b0caee4c2d5bd6e3b28779920516db3.tar.bz2 | |
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.c | 18 |
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(); } |