From: Omar Sandoval <[email protected]> When we insert a request, we set the software queue pending bit while holding the software queue lock. However, we clear it outside of the lock, so it's possible that a concurrent insert could reset the bit after we clear it but before we empty the request list. Afterwards, the bit would still be set but the software queue wouldn't have any requests in it, leading us to do a spurious run in the future. This is mostly a benign/theoretical issue, but it makes the following change easier to justify.
Signed-off-by: Omar Sandoval <[email protected]> --- block/blk-mq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 357492712b0e..09a57d97ca7f 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -984,9 +984,9 @@ static bool flush_busy_ctx(struct sbitmap *sb, unsigned int bitnr, void *data) struct blk_mq_hw_ctx *hctx = flush_data->hctx; struct blk_mq_ctx *ctx = hctx->ctxs[bitnr]; - sbitmap_clear_bit(sb, bitnr); spin_lock(&ctx->lock); list_splice_tail_init(&ctx->rq_list, flush_data->list); + sbitmap_clear_bit(sb, bitnr); spin_unlock(&ctx->lock); return true; } -- 2.16.2
