linux-kernel - Re: 2.6.22-rc6 spurious hangs

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Message-ID: <20070629131605.GA25964@elte.hu>
Date:	Fri, 29 Jun 2007 15:16:05 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Thomas Sattler <tsattler@....de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Daniel Mack <daniel@...u.de>, Holger Waechtler <holger@...u.de>
Subject: Re: 2.6.22-rc6 spurious hangs


* Oleg Nesterov <oleg@...sign.ru> wrote:

> Yes, I think cinergyt2 is buggy.

> cinergyt2_release() does flush_scheduled_work() under cinergyt2->sem. 
> flush_scheduled_work() hangs because cinergyt2_query_rc() waits for 
> the same cinergyt2->sem.
> 
> ->disconnect_pending is used without any locks/barriers, perhaps this 
> is the reason.
> 
> I'll try to look further tomorrow. In any case, cinergyT2 should not 
> use flush_scheduled_work() at all.

would the hack below be worth trying, to see whether there are any 
further problems?

	Ingo

Index: linux/drivers/media/dvb/cinergyT2/cinergyT2.c
===================================================================
--- linux.orig/drivers/media/dvb/cinergyT2/cinergyT2.c
+++ linux/drivers/media/dvb/cinergyT2/cinergyT2.c
@@ -523,7 +523,6 @@ static int cinergyt2_release (struct ino
 
 	if (!cinergyt2->disconnect_pending && (file->f_flags & O_ACCMODE) != O_RDONLY) {
 		cancel_delayed_work(&cinergyt2->query_work);
-		flush_scheduled_work();
 		cinergyt2_sleep(cinergyt2, 1);
 	}
 
@@ -974,8 +973,6 @@ static void cinergyt2_disconnect (struct
 {
 	struct cinergyt2 *cinergyt2 = usb_get_intfdata (intf);
 
-	flush_scheduled_work();
-
 	cinergyt2_unregister_rc(cinergyt2);
 
 	cancel_delayed_work(&cinergyt2->query_work);
@@ -1002,7 +999,6 @@ static int cinergyt2_suspend (struct usb
 		cancel_delayed_work(&cinergyt2->query_work);
 		if (cinergyt2->streaming)
 			cinergyt2_stop_stream_xfer(cinergyt2);
-		flush_scheduled_work();
 		cinergyt2_sleep(cinergyt2, 1);
 	}
 
-
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