There is a very tight race where the irq_retrigger function is run on one cpu and the actual retrigger softirq is running on a second cpu. When this happens, there may be a chance that the second cpu will not see the updated irq_pending value from first cpu. Add a memory barrier to ensure that irq_pending is read correctly. Signed-off-by: Chris Lew <quic_clew@xxxxxxxxxxx> --- drivers/soc/qcom/smp2p.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/soc/qcom/smp2p.c b/drivers/soc/qcom/smp2p.c index a94cddcb0298..a1ea5f55c228 100644 --- a/drivers/soc/qcom/smp2p.c +++ b/drivers/soc/qcom/smp2p.c @@ -249,6 +249,9 @@ static void qcom_smp2p_notify_in(struct qcom_smp2p *smp2p) status = val ^ entry->last_value; entry->last_value = val; + + /* Ensure irq_pending is read correctly */ + mb(); status |= *entry->irq_pending; /* No changes of this entry? */ @@ -356,6 +359,11 @@ static int smp2p_retrigger_irq(struct irq_data *irqd) set_bit(irq, entry->irq_pending); + /* Ensure irq_pending is visible to all cpus that retried interrupt + * can run on + */ + mb(); + return 0; } -- 2.7.4
