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Date: Mon, 21 Jul 2014 10:10:46 +0200 From: Alexander Gordeev <agordeev@...hat.com> To: linux-kernel@...r.kernel.org Cc: Alexander Gordeev <agordeev@...hat.com>, Jens Axboe <axboe@...nel.dk> Subject: [PATCH] blk-mq: bitmap tag: fix potential unwakeable sleep in bt_get() There is a race between __bt_get_word() and bt_clear_tag(). Since access to the tags bitmap is not serialized __bt_get_word() might miss a tag which is about to or being returned by bt_clear_tag(). As result, the process requesting the tag might end up schedulled out forever. To avoid this corner case call io_schedule_timeout() instead of io_schedule(). The timeout should be long enough to not falsely wake up waiters often, so take the requests queue's "rq_timeout" for that. Signed-off-by: Alexander Gordeev <agordeev@...hat.com> Cc: Jens Axboe <axboe@...nel.dk> --- block/blk-mq-tag.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index c1b9242..1785f1f 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -256,7 +256,7 @@ static int bt_get(struct blk_mq_alloc_data *data, blk_mq_put_ctx(data->ctx); - io_schedule(); + WARN_ON(!io_schedule_timeout(hctx->queue->rq_timeout)); data->ctx = blk_mq_get_ctx(data->q); data->hctx = data->q->mq_ops->map_queue(data->q, -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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