[PATCH 6.1 127/131] dmaengine: idxd: use spin_lock_irqsave before wait_event_lock_irq

Greg Kroah-Hartman
2023-10-16T09:06:07Z

From: Rex Zhang <rex.zhang@intel.com>

[ 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@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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/dma/idxd/device.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
index 3b4ad7739f9ee..188f6b8625f78 100644
--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -495,6 +495,7 @@ 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");
@@ -508,7 +509,7 @@ 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);
@@ -525,7 +526,7 @@ 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);
--
2.40.1