Attachment 309854 Details for Bug 444865 – updated patch

[patch] updated patch

20-bz-444865-cifs-don-t-allow-dem.patch (text/plain), 3.92 KB, created by Jeff Layton on 2008-06-19 15:29:18 UTC

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Creator: Jeff Layton

Created: 2008-06-19 15:29:18 UTC

Size: 3.92 KB

patch

obsolete

>BZ#444865: [CIFS] don't allow demultiplex thread to exit until kthread_stop is called
>
>From: Jeff Layton <jlayton@redhat.com>
>
>cifs_demultiplex_thread can exit under several conditions:
>
>1) if it's signaled
>2) if there's a problem with session setup
>3) if kthread_stop is called on it
>
>The first two are problems. If kthread_stop is called on the thread,
>there is no guarantee that it will still be up. We need to have the
>thread stay up until kthread_stop is called on it.
>
>One option would be to not even try to tear things down until after
>kthread_stop is called. However, in the case where there is a problem
>setting up the session, there's no real reason to try continuing the
>loop.
>
>This patch allows the thread to continue to exit its main loop under all
>three conditions, but it has the thread go to sleep until kthread_stop
>is called. This allows us to simplify the shutdown code somewhat since
>we can be reasonably sure that the thread won't exit after being
>signaled but before kthread_stop is called.
>
>It also removes the places where the thread itself set the tsk variable
>since it appeared that it could have a potential race where the thread
>might never be shut down.
>---
>
> fs/cifs/connect.c |   31 ++++++++++++++++---------------
> 1 files changed, 16 insertions(+), 15 deletions(-)
>
>
>diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
>index f6ffdf1..a41dc02 100644
>--- a/fs/cifs/connect.c
>+++ b/fs/cifs/connect.c
>@@ -375,7 +375,6 @@ cifs_demultiplex_thread(struct TCP_Server_Info *server)
> #endif
> 
> 	current->flags |= PF_MEMALLOC;
>-	server->tsk = current;	/* save process info to wake at shutdown */
> 	cFYI(1, ("Demultiplex PID: %d", current->pid));
> 	write_lock(&GlobalSMBSeslock);
> 	atomic_inc(&tcpSesAllocCount);
>@@ -701,14 +700,25 @@ multi_t2_fnd:
> #endif /* CIFS_DEBUG2 */
> 
> 		}
>-	} /* end while !EXITING */
>+	} /* end while !kthread_should_stop() */
> 
> 	spin_lock(&GlobalMid_Lock);
> 	server->tcpStatus = CifsExiting;
>-	server->tsk = NULL;
>+	spin_unlock(&GlobalMid_Lock);
>+	wake_up_all(&server->response_q);
>+
>+	/* don't exit until kthread_stop is called */
>+	set_current_state(TASK_UNINTERRUPTIBLE);
>+	while (!kthread_should_stop()) {
>+		schedule();
>+		set_current_state(TASK_UNINTERRUPTIBLE);
>+	}
>+	set_current_state(TASK_RUNNING);
>+
> 	/* check if we have blocked requests that need to free */
> 	/* Note that cifs_max_pending is normally 50, but
> 	can be set at module install time to as little as two */
>+	spin_lock(&GlobalMid_Lock);
> 	if (atomic_read(&server->inFlight) >= cifs_max_pending)
> 		atomic_set(&server->inFlight, cifs_max_pending - 1);
> 	/* We do not want to set the max_pending too low or we
>@@ -2268,15 +2278,12 @@ 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;
> 				/* If we could verify that kthread_stop would
> 				   always wake up processes blocked in
> 				   tcp in recv_mesg then we could remove the
> 				   send_sig call */
> 				force_sig(SIGKILL, srvTcp->tsk);
>-				tsk = srvTcp->tsk;
>-				if (tsk)
>-					kthread_stop(tsk);
>+				kthread_stop(srvTcp->tsk);
> 			}
> 		}
> 		 /* If find_unc succeeded then rc == 0 so we can not end */
>@@ -2292,23 +2299,17 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
> 					if ((temp_rc == -ESHUTDOWN) &&
> 					    (pSesInfo->server) &&
> 					    (pSesInfo->server->tsk)) {
>-						struct task_struct *tsk;
> 						force_sig(SIGKILL,
> 							pSesInfo->server->tsk);
>-						tsk = pSesInfo->server->tsk;
>-						if (tsk)
>-							kthread_stop(tsk);
>+						kthread_stop(pSesInfo->server->tsk);
> 					}
> 				} else {
> 					cFYI(1, ("No session or bad tcon"));
> 					if ((pSesInfo->server) &&
> 					    (pSesInfo->server->tsk)) {
>-						struct task_struct *tsk;
> 						force_sig(SIGKILL,
> 							pSesInfo->server->tsk);
>-						tsk = pSesInfo->server->tsk;
>-						if (tsk)
>-							kthread_stop(tsk);
>+						kthread_stop(pSesInfo->server->tsk);
> 					}
> 				}
> 				sesInfoFree(pSesInfo);

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