From b02f0c2ea25781e0f94b4fc8f6f85582057857b3 Mon Sep 17 00:00:00 2001 From: Jan Glauber Date: Sun, 24 Jul 2011 10:48:00 +0200 Subject: [PATCH] [S390] qdio: clear shared DSCI before scheduling the queue handler The following race can occur with qdio devices that use the shared device state change indicator: Device (Shared DSCI) CPU0 CPU1 =============================================================================== 1. DSCI 0 => 1, INT pending 2. Thinint handler * si_used = 1 * Inbound tasklet_schedule * DSCI 1 => 0 3. DSCI 0 => 1, INT pending 4. Thinint handler * si_used = 1 * Inbound tasklet_schedu le => NOP 5. Inbound tasklet run 6. DSCI = 1, INT surpressed 7. DSCI 1 => 0 The race would lead to a stall where new data in the input queue is not recognized so the device stops working in case of no further traffic. Fix the race by resetting the DSCI before scheduling the inbound tasklet so the device generates an interrupt if new data arrives in the above scenario in step 6. Reviewed-by: Ursula Braun Signed-off-by: Jan Glauber Signed-off-by: Martin Schwidefsky --- drivers/s390/cio/qdio_thinint.c | 15 +++++---------- 1 file changed, 5 insertions(+), 10 deletions(-) diff --git a/drivers/s390/cio/qdio_thinint.c b/drivers/s390/cio/qdio_thinint.c index 5c4e741d8221..68be6e157126 100644 --- a/drivers/s390/cio/qdio_thinint.c +++ b/drivers/s390/cio/qdio_thinint.c @@ -95,9 +95,11 @@ void tiqdio_remove_input_queues(struct qdio_irq *irq_ptr) } } -static inline u32 shared_ind_set(void) +static inline u32 clear_shared_ind(void) { - return q_indicators[TIQDIO_SHARED_IND].ind; + if (!atomic_read(&q_indicators[TIQDIO_SHARED_IND].count)) + return 0; + return xchg(&q_indicators[TIQDIO_SHARED_IND].ind, 0); } /** @@ -107,7 +109,7 @@ static inline u32 shared_ind_set(void) */ static void tiqdio_thinint_handler(void *alsi, void *data) { - u32 si_used = shared_ind_set(); + u32 si_used = clear_shared_ind(); struct qdio_q *q; last_ai_time = S390_lowcore.int_clock; @@ -150,13 +152,6 @@ static void tiqdio_thinint_handler(void *alsi, void *data) qperf_inc(q, adapter_int); } rcu_read_unlock(); - - /* - * If the shared indicator was used clear it now after all queues - * were processed. - */ - if (si_used && shared_ind_set()) - xchg(&q_indicators[TIQDIO_SHARED_IND].ind, 0); } static int set_subchannel_ind(struct qdio_irq *irq_ptr, int reset) -- 2.34.1