From: Jens Axboe <jaxboe@fusionio.com>
Date: Thu, 14 Jul 2011 10:45:13 +0000 (+0200)
Subject: Fix infinite loop on platforms with severely limited aio resources
X-Git-Tag: fio-1.57~2
X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=ccc02050c1a371385897aa964988dbab68597545

Fix infinite loop on platforms with severely limited aio resources

Problem hit on OSX, where with 4 jobs each with a queue depth larger
than what the system supports, you can get into a situation where
any given process can get EAGAIN on queueing AIO even if it has
nothing queued already. Check for this condition to avoid fio's
IO loop going into a death spiral.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
---

diff --git a/fio.c b/fio.c
index 9e9106d5..120431e9 100644
--- a/fio.c
+++ b/fio.c
@@ -550,9 +550,10 @@ sync_done:
 
 		/*
 		 * if we can queue more, do so. but check if there are
-		 * completed io_u's first.
+		 * completed io_u's first. Note that we can get BUSY even
+		 * without IO queued, if the system is resource starved.
 		 */
-		full = queue_full(td) || ret == FIO_Q_BUSY;
+		full = queue_full(td) || (ret == FIO_Q_BUSY && td->cur_depth);
 		if (full || !td->o.iodepth_batch_complete) {
 			min_events = min(td->o.iodepth_batch_complete,
 					 td->cur_depth);
@@ -710,9 +711,11 @@ sync_done:
 			break;
 
 		/*
-		 * See if we need to complete some commands
+		 * See if we need to complete some commands. Note that we
+		 * can get BUSY even without IO queued, if the system is
+		 * resource starved.
 		 */
-		full = queue_full(td) || ret == FIO_Q_BUSY;
+		full = queue_full(td) || (ret == FIO_Q_BUSY && td->cur_depth);
 		if (full || !td->o.iodepth_batch_complete) {
 			min_evts = min(td->o.iodepth_batch_complete,
 					td->cur_depth);