Re: [PATCH v2 1/7] libmultipath: fix tur checker locking

[Martin Wilck <mwilck@suse.com>]

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On Sat, 2018-02-10 at 00:28 +0100, Martin Wilck wrote:
> Maybe it's easier than we thought. Attached is a patch on top of
> yours that I think might work, please have a look. 
> 

That one didn't even compile. This one is better.

Martin

-- 
Dr. Martin Wilck <mwilck@suse.com>, Tel. +49 (0)911 74053 2107
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)

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From afb9c7de3658d49c4f28f6b9ee618a87b806ecdd Mon Sep 17 00:00:00 2001
From: Martin Wilck <mwilck@suse.com>
Date: Sat, 10 Feb 2018 00:22:17 +0100
Subject: [PATCH] tur checker: make sure pthread_cancel isn't called for exited
 thread

If we enter the cleanup function as the result of a pthread_cancel by another
thread, we don't need to wait for a cancellation any more. If we exit
regularly, just tell the other thread not to try to cancel us.
---
 libmultipath/checkers/tur.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/libmultipath/checkers/tur.c b/libmultipath/checkers/tur.c
index 894ad41c89c3..5d2b36bfa883 100644
--- a/libmultipath/checkers/tur.c
+++ b/libmultipath/checkers/tur.c
@@ -214,15 +214,13 @@ retry:
 
 static void cleanup_func(void *data)
 {
-	int running, holders;
+	int holders;
 	struct tur_checker_context *ct = data;
 
-	running = uatomic_xchg(&ct->running, 0);
+	uatomic_set(&ct->running, 0);
 	holders = uatomic_sub_return(&ct->holders, 1);
 	if (!holders)
 		cleanup_context(ct);
-	if (!running)
-		pause();
 }
 
 static int tur_running(struct tur_checker_context *ct)
@@ -266,6 +264,9 @@ static void *tur_thread(void *ctx)
 	pthread_cond_signal(&ct->active);
 	pthread_mutex_unlock(&ct->lock);
 
+	/* Tell main checker thread not to cancel us, as we exit anyway */
+	uatomic_set(&ct->running, 0);
+
 	condlog(3, "%s: tur checker finished, state %s",
 		tur_devt(devt, sizeof(devt), ct), checker_state_name(state));
 	tur_thread_cleanup_pop(ct);
-- 
2.16.1


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