Patch "dmaengine: idxd: use spin_lock_irqsave before wait_event_lock_irq" has been added to the 5.15-stable tree

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This is a note to let you know that I've just added the patch titled

    dmaengine: idxd: use spin_lock_irqsave before wait_event_lock_irq

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dmaengine-idxd-use-spin_lock_irqsave-before-wait_eve.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 12d3a3a7120a0c1184f2f453d7c5449f16d441a0
Author: Rex Zhang <rex.zhang@xxxxxxxxx>
Date:   Sat Sep 16 14:06:19 2023 +0800

    dmaengine: idxd: use spin_lock_irqsave before wait_event_lock_irq
    
    [ Upstream commit c0409dd3d151f661e7e57b901a81a02565df163c ]
    
    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@xxxxxxxxx>
    Signed-off-by: Lijun Pan <lijun.pan@xxxxxxxxx>
    Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
    Reviewed-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
    Link: https://lore.kernel.org/r/20230916060619.3744220-1-rex.zhang@xxxxxxxxx
    Signed-off-by: Vinod Koul <vkoul@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
index 535f021911c55..f2cfefc505a8c 100644
--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -490,6 +490,7 @@ 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");
@@ -503,7 +504,7 @@ 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);
@@ -520,7 +521,7 @@ 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);



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