dmaengine: idxd: use spin_lock_irqsave before wait_event_lock_irq

In idxd_cmd_exec(), wait_event_lock_irq() explicitly calls
spin_unlock_irq()/spin_lock_irq(). If the interrupt is on before entering
wait_event_lock_irq(), it will become off status after
wait_event_lock_irq() is called. Later, wait_for_completion() may go to
sleep but irq is disabled. The scenario is warned in might_sleep().

Fix it by using spin_lock_irqsave() instead of the primitive spin_lock()
to save the irq status before entering wait_event_lock_irq() and using
spin_unlock_irqrestore() instead of the primitive spin_unlock() to restore
the irq status before entering wait_for_completion().

Before the change:
idxd_cmd_exec() {
interrupt is on
spin_lock()                        // interrupt is on
	wait_event_lock_irq()
		spin_unlock_irq()  // interrupt is enabled
		...
		spin_lock_irq()    // interrupt is disabled
spin_unlock()                      // interrupt is still disabled
wait_for_completion()              // report "BUG: sleeping function
				   // called from invalid context...
				   // in_atomic() irqs_disabled()"
}

After applying spin_lock_irqsave():
idxd_cmd_exec() {
interrupt is on
spin_lock_irqsave()                // save the on state
				   // interrupt is disabled
	wait_event_lock_irq()
		spin_unlock_irq()  // interrupt is enabled
		...
		spin_lock_irq()    // interrupt is disabled
spin_unlock_irqrestore()           // interrupt is restored to on
wait_for_completion()              // No Call trace
}

Fixes: f9f4082dbc56 ("dmaengine: idxd: remove interrupt disable for cmd_lock")
Signed-off-by: Rex Zhang <rex.zhang@intel.com>
Signed-off-by: Lijun Pan <lijun.pan@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Link: https://lore.kernel.org/r/20230916060619.3744220-1-rex.zhang@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
index 22d6f4e455b7973cae80208ccfcd638f3e0e0dca..8f754f922217dedb7b49d2991d85b007201331ac 100644 (file)
--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -477,6 +477,7 @@ static void idxd_cmd_exec(struct idxd_device *idxd, int cmd_code, u32 operand,
        union idxd_command_reg cmd;
        DECLARE_COMPLETION_ONSTACK(done);
        u32 stat;
+       unsigned long flags;
 
        if (idxd_device_is_halted(idxd)) {
                dev_warn(&idxd->pdev->dev, "Device is HALTED!\n");
@@ -490,7 +491,7 @@ static void idxd_cmd_exec(struct idxd_device *idxd, int cmd_code, u32 operand,
        cmd.operand = operand;
        cmd.int_req = 1;
 
-       spin_lock(&idxd->cmd_lock);
+       spin_lock_irqsave(&idxd->cmd_lock, flags);
        wait_event_lock_irq(idxd->cmd_waitq,
                            !test_bit(IDXD_FLAG_CMD_RUNNING, &idxd->flags),
                            idxd->cmd_lock);
@@ -507,7 +508,7 @@ static void idxd_cmd_exec(struct idxd_device *idxd, int cmd_code, u32 operand,
         * After command submitted, release lock and go to sleep until
         * the command completes via interrupt.
         */
-       spin_unlock(&idxd->cmd_lock);
+       spin_unlock_irqrestore(&idxd->cmd_lock, flags);
        wait_for_completion(&done);
        stat = ioread32(idxd->reg_base + IDXD_CMDSTS_OFFSET);
        spin_lock(&idxd->cmd_lock);