linux-kernel - Re: 2.6.22-rc1-mm1 cifs

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Date:	Wed, 23 May 2007 17:14:42 -0500
From:	Steven French <sfrench@...ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	David Kleikamp <shaggy@...ibm.com>,
	"young dave" <hidave.darkstar@...il.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	Shirish S Pargaonkar <shirishp@...ibm.com>
Subject: Re: 2.6.22-rc1-mm1 cifs_mount oops

> This can end up running kthread_stop() against an already-exited task.
I don't think so since cifs_demultiplex_thread waits sufficiently long 
before 
exit but after setting srvTcp->tsk to zero (the wait is immediately after 
waking up any processes that may be blocked on requests on this socket to 
give
file requests time to exit from the cifs vfs).   As long as this (mount) 
process were 
scheduled within 1.25 seconds it should be ok although more complicated 
than I
would like (that is why this thread was the last one in cifs to switch
to kthread API).

I wish there were an obvious way to do this, perhaps without using 
kthread_stop at all
for this thread (since that by itself does not seem to work for threads 
blocked 
in various socket calls).


--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2069,8 +2069,12 @@ cifs_mount(struct super_block *sb, struct 
cifs_sb_info *cifs_sb,
                                                 srvTcp->tcpStatus = 
CifsExiting;
 spin_unlock(&GlobalMid_Lock);
                                                 if (srvTcp->tsk) {
                                                                 struct 
task_struct *tsk;
 send_sig(SIGKILL,srvTcp->tsk,1);
- kthread_stop(srvTcp->tsk);
+                                                                /* 
srvTcp->tsk can be zeroed at any time */
+                                                                tsk = 
srvTcp->tsk;
+                                                                if (tsk)
+  kthread_stop(tsk);
                                                 }


I don't think so 


Steve French
Senior Software Engineer
Linux Technology Center - IBM Austin
phone: 512-838-2294
email: sfrench at-sign us dot ibm dot com
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