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Date: Wed, 23 May 2007 21:38:35 -0500
From: Steven French <sfrench@...ibm.com>
To: "young dave" <hidave.darkstar@...il.com>
Cc: "Andrew Morton" <akpm@...ux-foundation.org>,
David Kleikamp <shaggy@...ibm.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
If srvTcp->tsk is NULL then the thread (cifs_demultiplex_thread) is
getting ready to exit and kthread_stop would not be needed.
It would probably be possible to recode this so we don't need to call
kthread_stop at all (send_sig is apparently required to wake up this
thread when blocked in certain places in the tcp stack - and in
combination with the existing flags might be good enough) - but I don't
know if it would make it simpler. Fortunately there is no race, a few
lines after srvTcp->tsk is set to zero by the cifs_demultipex_thread, it
will sleep briefly before exiting (kthread_stop won't be called on a
thread that does not exist).
That section of code in fs/cifs/connect.c now looks like:
2071 if (srvTcp->tsk) {
2072 struct task_struct *tsk;
2073
/* If we could verify that kthread_stop would
2074
always wake up processes blocked in
2075
tcp in recv_mesg then we could remove the
2076 send_sig call */
2077 send_sig(SIGKILL,srvTcp->tsk,1);
2078 tsk = srvTcp->tsk;
2079 if(tsk)
2080 kthread_stop(srvTcp->tsk);
2081 }
2082 }
2083
/* If find_unc succeeded then rc == 0 so we can not end */
2084
if (tcon) /* up accidently freeing someone elses tcon struct */
2085 tconInfoFree(tcon);
2086 if (existingCifsSes == NULL) {
2087 if (pSesInfo) {
2088 if ((pSesInfo->server) &&
2089 (pSesInfo->status == CifsGood)) {
2090 int temp_rc;
2091
temp_rc = CIFSSMBLogoff(xid, pSesInfo);
2092
/* if the socketUseCount is now zero */
2093
if ((temp_rc == -ESHUTDOWN) &&
2094
(pSesInfo->server) && (pSesInfo->server->tsk)) {
2095
struct task_struct *tsk;
2096
send_sig(SIGKILL,pSesInfo->server->tsk,1);
2097
tsk = pSesInfo->server->tsk;
2098 if(tsk)
2099
kthread_stop(tsk);
Steve French
Senior Software Engineer
Linux Technology Center - IBM Austin
phone: 512-838-2294
email: sfrench at-sign us dot ibm dot com
"young dave" <hidave.darkstar@...il.com>
05/23/2007 08:05 PM
To
Steven French/Austin/IBM@...US
cc
"Andrew Morton" <akpm@...ux-foundation.org>, David
Kleikamp/Austin/IBM@...US, "Linux Kernel Mailing List"
<linux-kernel@...r.kernel.org>, Shirish S Pargaonkar/Austin/IBM@...US
Subject
Re: 2.6.22-rc1-mm1 cifs_mount oops
Hi,
I have one problem about this: after the srvTcp->tsk is set to NULL
(maybe the thread is still there, isn't it?), is the kthread still
needed to be stopped by calling kthread_stop()? If it is true, then
the task_struct should be saved before send_sig like my patch:
if (srvTcp->tsk) {
+ struct task_struct * tsk = srvTcp->tsk;
send_sig(SIGKILL,srvTcp->tsk,1);
- kthread_stop(srvTcp->tsk);
+ kthread_stop(tsk);
Regards
dave
-
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