Commit 2a236122 authored Aug 23, 2014 by Thorsten Knabe Committed by Richard Weinberger Oct 13, 2014

um: ubd: Fix for processes stuck in D state forever



Starting with Linux 3.12 processes get stuck in D state forever in
UserModeLinux under sync heavy workloads. This bug was introduced by
commit 805f11a0 (um: ubd: Add REQ_FLUSH suppport).
Fix bug by adding a check if FLUSH request was successfully submitted to
the I/O thread and keeping the FLUSH request on the request queue on
submission failures.

Fixes: 805f11a0 (um: ubd: Add REQ_FLUSH suppport)
Signed-off-by: Thorsten Knabe <linux@thorsten-knabe.de>
Cc: stable@kernel.org # >= 3.12
Signed-off-by: Richard Weinberger <richard@nod.at>

parent 9e6a57d2

arch/um/drivers/ubd_kern.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -1277,7 +1277,7 @@ static void do_ubd_request(struct request_queue *q)

		while(1){
		struct ubd *dev = q->queuedata;
		if(dev->end_sg == 0){
		if(dev->request == NULL){
		struct request *req = blk_fetch_request(q);
		if(req == NULL)
		return;
		@@ -1299,7 +1299,8 @@ static void do_ubd_request(struct request_queue *q)
		return;
		}
		prepare_flush_request(req, io_req);
		submit_request(io_req, dev);
		if (submit_request(io_req, dev) == false)
		return;
		}

		while(dev->start_sg < dev->end_sg){