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author | 2010-07-27 19:29:38 +0200 | |
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committer | 2010-07-27 19:29:42 +0200 | |
commit | 33fea794b9deeb8ffb77e284eb37375b8f45a2c4 (patch) | |
tree | 4a9a1cbad368c1f6c2c79e334c68f8ca04721b98 /arch/s390 | |
parent | [S390] Fix IRQ tracing in case of PER (diff) | |
download | linux-33fea794b9deeb8ffb77e284eb37375b8f45a2c4.tar.gz linux-33fea794b9deeb8ffb77e284eb37375b8f45a2c4.tar.bz2 linux-33fea794b9deeb8ffb77e284eb37375b8f45a2c4.zip |
[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>
Diffstat (limited to 'arch/s390')
-rw-r--r-- | arch/s390/kernel/time.c | 18 |
1 files changed, 12 insertions, 6 deletions
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c index a2163c95eb98..15a7536452d5 100644 --- a/arch/s390/kernel/time.c +++ b/arch/s390/kernel/time.c @@ -524,8 +524,11 @@ void etr_switch_to_local(void) if (!etr_eacr.sl) return; disable_sync_clock(NULL); - set_bit(ETR_EVENT_SWITCH_LOCAL, &etr_events); - queue_work(time_sync_wq, &etr_work); + if (!test_and_set_bit(ETR_EVENT_SWITCH_LOCAL, &etr_events)) { + etr_eacr.es = etr_eacr.sl = 0; + etr_setr(&etr_eacr); + queue_work(time_sync_wq, &etr_work); + } } /* @@ -539,8 +542,11 @@ void etr_sync_check(void) if (!etr_eacr.es) return; disable_sync_clock(NULL); - set_bit(ETR_EVENT_SYNC_CHECK, &etr_events); - queue_work(time_sync_wq, &etr_work); + if (!test_and_set_bit(ETR_EVENT_SYNC_CHECK, &etr_events)) { + etr_eacr.es = 0; + etr_setr(&etr_eacr); + queue_work(time_sync_wq, &etr_work); + } } /* @@ -902,7 +908,7 @@ static struct etr_eacr etr_handle_update(struct etr_aib *aib, * Do not try to get the alternate port aib if the clock * is not in sync yet. */ - if (!check_sync_clock()) + if (!eacr.es || !check_sync_clock()) return eacr; /* @@ -1064,7 +1070,7 @@ static void etr_work_fn(struct work_struct *work) * If the clock is in sync just update the eacr and return. * If there is no valid sync port wait for a port update. */ - if (check_sync_clock() || sync_port < 0) { + if ((eacr.es && check_sync_clock()) || sync_port < 0) { etr_update_eacr(eacr); etr_set_tolec_timeout(now); goto out_unlock; |