From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:60045) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SSRsx-0002Qa-FB for qemu-devel@nongnu.org; Thu, 10 May 2012 07:50:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SSRsq-0006WR-4n for qemu-devel@nongnu.org; Thu, 10 May 2012 07:50:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37802) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SSRsp-0006W2-TZ for qemu-devel@nongnu.org; Thu, 10 May 2012 07:50:12 -0400 From: Kevin Wolf Date: Thu, 10 May 2012 13:49:31 +0200 Message-Id: <1336650574-12835-28-git-send-email-kwolf@redhat.com> In-Reply-To: <1336650574-12835-1-git-send-email-kwolf@redhat.com> References: <1336650574-12835-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PATCH 27/30] stream: fix ratelimiting corner case List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: anthony@codemonkey.ws Cc: kwolf@redhat.com, qemu-devel@nongnu.org From: Paolo Bonzini This fixes inability to make progress in streaming if the quota is set to less than the amount of data that an I/O operation has to write. In this case, limit->dispatched + n will always be above the quota and, due to the "goto retry" to recheck cancellation and allocation, streaming will livelock. This can be reproduced with "block_job_set_speed ide0-hd0 1b". Of course, with this patch the requested limit will not be obeyed. That could be done with another patch that caps is_allocated's n argument by the slice quota. Signed-off-by: Paolo Bonzini Signed-off-by: Kevin Wolf --- block/stream.c | 10 +++++----- 1 files changed, 5 insertions(+), 5 deletions(-) diff --git a/block/stream.c b/block/stream.c index 25f98e4..a2c8f67 100644 --- a/block/stream.c +++ b/block/stream.c @@ -33,19 +33,19 @@ typedef struct { static int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n) { - int64_t delay_ns = 0; int64_t now = qemu_get_clock_ns(rt_clock); if (limit->next_slice_time < now) { limit->next_slice_time = now + SLICE_TIME; limit->dispatched = 0; } - if (limit->dispatched + n > limit->slice_quota) { - delay_ns = limit->next_slice_time - now; - } else { + if (limit->dispatched == 0 || limit->dispatched + n <= limit->slice_quota) { limit->dispatched += n; + return 0; + } else { + limit->dispatched = n; + return limit->next_slice_time - now; } - return delay_ns; } static void ratelimit_set_speed(RateLimit *limit, uint64_t speed) -- 1.7.6.5