I recently sent a similar, smaller patch for this problem. After some
discussion with Steve and Shaggy, I think I better understand why cifsd
allows signals through, and I realize that my earlier patch wasn't
comprehensive enough
The mount and unmount calls will send a KILL signal to cifsd to wake it
up if it happens to be blocked in kernel_recvmsg. The problem is that
it doesn't distinguish between "legitimate" signals sent for this
reason and spurious signals sent by a userspace process (for instance).
While this is definitely a "don't do that" sort of situation, we might
as well try to have cifsd be as signal-safe as possible.
The following patch does this by making sure that we set tcpStatus to
CifsExiting before sending cifsd a signal, and having cifsd check for
that when it sees that it's been signalled. If the tcpStatus is not set
correctly, it ignores it, flushes signals and moves on.
I've tested a similar backported version of this on an earlier kernel,
but have not tested this particular patch as of yet.
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index f4e9266..461fbaa 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -197,6 +197,11 @@ cifs_reconnect(struct TCP_Server_Info *server)
server->server_RFC1001_name);
}
if(rc) {
+ if (rc == -ERESTARTSYS) {
+ cFYI(1,("reconnect interrupted by signal"));
+ flush_signals(server->tsk);
+ continue;
+ }
cFYI(1,("reconnect error %d",rc));
msleep(3000);
} else {
@@ -425,8 +430,14 @@ cifs_demultiplex_thread(struct TCP_Server_Info *server)
break;
}
if (!try_to_freeze() && (length == -EINTR)) {
- cFYI(1,("cifsd thread killed"));
- break;
+ if (server->tcpStatus == CifsExiting) {
+ cFYI(1,("cifsd thread killed"));
+ break;
+ } else {
+ cFYI(1,("cifsd caught spurious signal, ignoring it"));
+ flush_signals(server->tsk);
+ continue;
+ }
}
cFYI(1,("Reconnect after unexpected peek error %d",
length));
@@ -526,11 +537,15 @@ cifs_demultiplex_thread(struct TCP_Server_Info *server)
total_read += length) {
length = kernel_recvmsg(csocket, &smb_msg, &iov, 1,
pdu_length - total_read, 0);
- if( kthread_should_stop() ||
- (length == -EINTR)) {
- /* then will exit */
+ if (kthread_should_stop() ||
+ (length == -EINTR &&
+ server->tcpStatus == CifsExiting)) {
reconnect = 2;
break;
+ } else if (length == -EINTR) {
+ cFYI(1, ("cifsd caught spurious signal, ignoring it"));
+ flush_signals(server->tsk);
+ continue;
} else if (server->tcpStatus == CifsNeedReconnect) {
cifs_reconnect(server);
csocket = server->ssocket;
@@ -1692,6 +1707,26 @@ void reset_cifs_unix_caps(int xid, struct cifsTconInfo * tcon,
}
}
+static inline void stop_cifsd(struct TCP_Server_Info *srv)
+{
+ struct task_struct *tsk = srv->tsk;
+
+ cFYI(1,("shutting down cifsd thread"));
+
+ spin_lock(&GlobalMid_Lock);
+ srv->tcpStatus = CifsExiting;
+ spin_unlock(&GlobalMid_Lock);
+
+ /* 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 */
+ send_sig(SIGKILL, tsk, 1);
+
+ if (tsk)
+ kthread_stop(tsk);
+}
+
int
cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
char *mount_data, const char *devname)
@@ -2064,22 +2099,9 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
if (rc) {
/* if session setup failed, use count is zero but
we still need to free cifsd thread */
- if (atomic_read(&srvTcp->socketUseCount) == 0) {
- spin_lock(&GlobalMid_Lock);
- 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 */
- send_sig(SIGKILL,srvTcp->tsk,1);
- tsk = srvTcp->tsk;
- if(tsk)
- kthread_stop(tsk);
- }
- }
+ if (atomic_read(&srvTcp->socketUseCount) == 0)
+ stop_cifsd(srvTcp);
+
/* If find_unc succeeded then rc == 0 so we can not end */
if (tcon) /* up accidently freeing someone elses tcon struct */
tconInfoFree(tcon);
@@ -2091,13 +2113,8 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
temp_rc = CIFSSMBLogoff(xid, pSesInfo);
/* if the socketUseCount is now zero */
if ((temp_rc == -ESHUTDOWN) &&
- (pSesInfo->server) && (pSesInfo->server->tsk)) {
- struct task_struct *tsk;
- send_sig(SIGKILL,pSesInfo->server->tsk,1);
- tsk = pSesInfo->server->tsk;
- if (tsk)
- kthread_stop(tsk);
- }
+ (pSesInfo->server) && (pSesInfo->server->tsk))
+ stop_cifsd(pSesInfo->server);
} else
cFYI(1, ("No session or bad tcon"));
sesInfoFree(pSesInfo);
@@ -3321,7 +3338,7 @@ cifs_umount(struct super_block *sb, struct cifs_sb_info *cifs_sb)
int rc = 0;
int xid;
struct cifsSesInfo *ses = NULL;
- struct task_struct *cifsd_task;
+ struct TCP_Server_Info *server;
char * tmp;
xid = GetXid();
@@ -3335,19 +3352,15 @@ cifs_umount(struct super_block *sb, struct cifs_sb_info *cifs_sb)
}
tconInfoFree(cifs_sb->tcon);
if ((ses) && (ses->server)) {
- /* save off task so we do not refer to ses later */
- cifsd_task = ses->server->tsk;
+ /* save off server so we do not refer to ses later */
+ server = ses->server;
cFYI(1, ("About to do SMBLogoff "));
rc = CIFSSMBLogoff(xid, ses);
if (rc == -EBUSY) {
FreeXid(xid);
return 0;
} else if (rc == -ESHUTDOWN) {
- cFYI(1,("Waking up socket by sending it signal"));
- if (cifsd_task) {
- send_sig(SIGKILL,cifsd_task,1);
- kthread_stop(cifsd_task);
- }
+ stop_cifsd(server);
rc = 0;
} /* else - we have an smb session
left on this socket do not kill cifsd */
-
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