From 81a9c5e72bdf7109a65102ca61d8cbd722cf4021 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Mon, 23 Jun 2014 13:42:37 -0400 Subject: [PATCH] iscsi-target: fix iscsit_del_np deadlock on unload 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 Cc: stable@vger.kernel.org Signed-off-by: Nicholas Bellinger --- drivers/target/iscsi/iscsi_target_login.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c index fecb69535a15..5e71ac609418 100644 --- a/drivers/target/iscsi/iscsi_target_login.c +++ b/drivers/target/iscsi/iscsi_target_login.c @@ -1216,7 +1216,7 @@ 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; @@ -1230,6 +1230,9 @@ 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; } @@ -1422,10 +1425,8 @@ 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); @@ -1442,7 +1443,7 @@ 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 -- 2.39.5