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| author | Mikulas Patocka <mpatocka@redhat.com> | 2014-06-23 13:42:37 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-07-06 18:57:26 -0700 |
| commit | a36b04d7a94ae3568334d36ad9a229671fbb11ab (patch) | |
| tree | a8c869fe1d0151b4517c1ffb6509de3330894456 | |
| parent | 2cfffbdaa8cbe4262216bf28f3eb173cfe4a91d3 (diff) | |
| download | lwn-a36b04d7a94ae3568334d36ad9a229671fbb11ab.tar.gz lwn-a36b04d7a94ae3568334d36ad9a229671fbb11ab.zip | |
iscsi-target: fix iscsit_del_np deadlock on unload
commit 81a9c5e72bdf7109a65102ca61d8cbd722cf4021 upstream.
On uniprocessor preemptible kernel, target core deadlocks on unload. The
following events happen:
* iscsit_del_np is called
* it calls send_sig(SIGINT, np->np_thread, 1);
* the scheduler switches to the np_thread
* the np_thread is woken up, it sees that kthread_should_stop() returns
false, so it doesn't terminate
* the np_thread clears signals with flush_signals(current); and goes back
to sleep in iscsit_accept_np
* the scheduler switches back to iscsit_del_np
* iscsit_del_np calls kthread_stop(np->np_thread);
* the np_thread is waiting in iscsit_accept_np and it doesn't respond to
kthread_stop
The deadlock could be resolved if the administrator sends SIGINT signal to
the np_thread with killall -INT iscsi_np
The reproducible deadlock was introduced in commit
db6077fd0b7dd41dc6ff18329cec979379071f87, but the thread-stopping code was
racy even before.
This patch fixes the problem. Using kthread_should_stop to stop the
np_thread is unreliable, so we test np_thread_state instead. If
np_thread_state equals ISCSI_NP_THREAD_SHUTDOWN, the thread exits.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/target/iscsi/iscsi_target_login.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c index cad6fdcc64da..d509aa74cfa1 100644 --- a/drivers/target/iscsi/iscsi_target_login.c +++ b/drivers/target/iscsi/iscsi_target_login.c @@ -1196,7 +1196,7 @@ old_sess_out: static int __iscsi_target_login_thread(struct iscsi_np *np) { u8 *buffer, zero_tsih = 0; - int ret = 0, rc, stop; + int ret = 0, rc; struct iscsi_conn *conn = NULL; struct iscsi_login *login; struct iscsi_portal_group *tpg = NULL; @@ -1210,6 +1210,9 @@ static int __iscsi_target_login_thread(struct iscsi_np *np) if (np->np_thread_state == ISCSI_NP_THREAD_RESET) { np->np_thread_state = ISCSI_NP_THREAD_ACTIVE; complete(&np->np_restart_comp); + } else if (np->np_thread_state == ISCSI_NP_THREAD_SHUTDOWN) { + spin_unlock_bh(&np->np_thread_lock); + goto exit; } else { np->np_thread_state = ISCSI_NP_THREAD_ACTIVE; } @@ -1402,10 +1405,8 @@ old_sess_out: } out: - stop = kthread_should_stop(); - /* Wait for another socket.. */ - if (!stop) - return 1; + return 1; + exit: iscsi_stop_login_thread_timer(np); spin_lock_bh(&np->np_thread_lock); @@ -1422,7 +1423,7 @@ int iscsi_target_login_thread(void *arg) allow_signal(SIGINT); - while (!kthread_should_stop()) { + while (1) { ret = __iscsi_target_login_thread(np); /* * We break and exit here unless another sock_accept() call |