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
db6077fd0b
, 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>
This commit is contained in:
parent
ac5ccdba3a
commit
81a9c5e72b
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@ -1216,7 +1216,7 @@ old_sess_out:
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static int __iscsi_target_login_thread(struct iscsi_np *np)
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{
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u8 *buffer, zero_tsih = 0;
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int ret = 0, rc, stop;
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int ret = 0, rc;
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struct iscsi_conn *conn = NULL;
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struct iscsi_login *login;
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struct iscsi_portal_group *tpg = NULL;
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@ -1230,6 +1230,9 @@ static int __iscsi_target_login_thread(struct iscsi_np *np)
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if (np->np_thread_state == ISCSI_NP_THREAD_RESET) {
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np->np_thread_state = ISCSI_NP_THREAD_ACTIVE;
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complete(&np->np_restart_comp);
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} else if (np->np_thread_state == ISCSI_NP_THREAD_SHUTDOWN) {
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spin_unlock_bh(&np->np_thread_lock);
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goto exit;
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} else {
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np->np_thread_state = ISCSI_NP_THREAD_ACTIVE;
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}
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@ -1422,10 +1425,8 @@ old_sess_out:
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}
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out:
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stop = kthread_should_stop();
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/* Wait for another socket.. */
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if (!stop)
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return 1;
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exit:
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iscsi_stop_login_thread_timer(np);
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spin_lock_bh(&np->np_thread_lock);
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@ -1442,7 +1443,7 @@ int iscsi_target_login_thread(void *arg)
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allow_signal(SIGINT);
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while (!kthread_should_stop()) {
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while (1) {
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ret = __iscsi_target_login_thread(np);
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/*
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* We break and exit here unless another sock_accept() call
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