[S390] etr: fix clock synchronization race
The etr events switch-to-local and sync-check disable the synchronous clock and schedule a work queue that tries to get the clock back into sync. If another switch-to-local or sync-check event occurs while the work queue function etr_work_fn still runs the eacr.es bit and the clock_sync_word can become inconsistent because check_sync_clock only uses the clock_sync_word to determine if the clock is in sync or not. The second pass of the etr_work_fn will reset the eacr.es bit but will leave the clock_sync_word intact. Fix this race by moving the reset of the eacr.es bit into the switch-to-local and sync-check functions and by checking the eacr.es bit as well to decide if the clock needs to be synced. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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@ -524,8 +524,11 @@ void etr_switch_to_local(void)
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if (!etr_eacr.sl)
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return;
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disable_sync_clock(NULL);
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set_bit(ETR_EVENT_SWITCH_LOCAL, &etr_events);
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queue_work(time_sync_wq, &etr_work);
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if (!test_and_set_bit(ETR_EVENT_SWITCH_LOCAL, &etr_events)) {
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etr_eacr.es = etr_eacr.sl = 0;
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etr_setr(&etr_eacr);
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queue_work(time_sync_wq, &etr_work);
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}
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}
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/*
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@ -539,8 +542,11 @@ void etr_sync_check(void)
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if (!etr_eacr.es)
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return;
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disable_sync_clock(NULL);
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set_bit(ETR_EVENT_SYNC_CHECK, &etr_events);
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queue_work(time_sync_wq, &etr_work);
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if (!test_and_set_bit(ETR_EVENT_SYNC_CHECK, &etr_events)) {
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etr_eacr.es = 0;
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etr_setr(&etr_eacr);
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queue_work(time_sync_wq, &etr_work);
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}
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}
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/*
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@ -902,7 +908,7 @@ static struct etr_eacr etr_handle_update(struct etr_aib *aib,
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* Do not try to get the alternate port aib if the clock
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* is not in sync yet.
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*/
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if (!check_sync_clock())
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if (!eacr.es || !check_sync_clock())
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return eacr;
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/*
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@ -1064,7 +1070,7 @@ static void etr_work_fn(struct work_struct *work)
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* If the clock is in sync just update the eacr and return.
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* If there is no valid sync port wait for a port update.
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*/
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if (check_sync_clock() || sync_port < 0) {
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if ((eacr.es && check_sync_clock()) || sync_port < 0) {
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etr_update_eacr(eacr);
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etr_set_tolec_timeout(now);
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goto out_unlock;
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