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authorMikulas Patocka <mpatocka@redhat.com>2014-06-23 13:42:37 -0400
committerNicholas Bellinger <nab@linux-iscsi.org>2014-06-27 23:23:35 -0700
commit81a9c5e72bdf7109a65102ca61d8cbd722cf4021 (patch)
tree23e1accddfc6aedef0186db3061fe820b023dfc7
parentac5ccdba3a1659b3517e7e99ef7d35a6a2d77cf4 (diff)
downloadlinux-stericsson-81a9c5e72bdf7109a65102ca61d8cbd722cf4021.tar.gz
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 <mpatocka@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
-rw-r--r--drivers/target/iscsi/iscsi_target_login.c13
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 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