habanalabs: fix race between wait and irq

There is a race in the user interrupts code, where between checking
the target value and adding the new pend to the list, there is a chance
the interrupt happened.

In that case, no one will complete the node, and we will get a timeout
on it.

Signed-off-by: Oded Gabbay <ogabbay@kernel.org>

diff --git a/drivers/misc/habanalabs/common/command_submission.c b/drivers/misc/habanalabs/common/command_submission.c
index 8dd2f39..307a95a 100644 (file)
--- a/drivers/misc/habanalabs/common/command_submission.c
+++ b/drivers/misc/habanalabs/common/command_submission.c
@@ -2892,16 +2892,21 @@ static int _hl_interrupt_wait_ioctl(struct hl_device *hdev, struct hl_ctx *ctx,
        pend->cq_kernel_addr = (u64 *) cb->kernel_address + cq_counters_offset;
        pend->cq_target_value = target_value;
 
+       spin_lock_irqsave(&interrupt->wait_list_lock, flags);
+
        /* We check for completion value as interrupt could have been received
         * before we added the node to the wait list
         */
        if (*pend->cq_kernel_addr >= target_value) {
+               spin_unlock_irqrestore(&interrupt->wait_list_lock, flags);
+
                *status = HL_WAIT_CS_STATUS_COMPLETED;
                /* There was no interrupt, we assume the completion is now. */
                pend->fence.timestamp = ktime_get();
                goto set_timestamp;
 
        } else if (!timeout_us) {
+               spin_unlock_irqrestore(&interrupt->wait_list_lock, flags);
                *status = HL_WAIT_CS_STATUS_BUSY;
                pend->fence.timestamp = ktime_get();
                goto set_timestamp;
@@ -2910,7 +2915,6 @@ static int _hl_interrupt_wait_ioctl(struct hl_device *hdev, struct hl_ctx *ctx,
        /* Add pending user interrupt to relevant list for the interrupt
         * handler to monitor
         */
-       spin_lock_irqsave(&interrupt->wait_list_lock, flags);
        list_add_tail(&pend->wait_list_node, &interrupt->wait_list_head);
        spin_unlock_irqrestore(&interrupt->wait_list_lock, flags);