[Intel-wired-lan] [PATCH net v2 1/2] ixgbe: do not busy wait in ixgbe_devlink_reload_empr_finish()

[Linkui Xiao]

From: Linkui Xiao <xiaolinkui@xxxxxxxxxx>

ixgbe_devlink_reload_empr_finish() is the .reload_up devlink operation,
so it always runs in process context with the devlink instance lock held.
Its polling loop delays with mdelay(500), i.e. it spins the CPU for half
a second per iteration and, because the loop bound is 20 iterations, for
up to ten seconds. That keeps a CPU fully occupied while the firmware
performs the EMP reset, and on CONFIG_PREEMPT_NONE it also makes the
loop non-preemptible for that whole window. The loop does not need to be
atomic and holds no spinlock.

Use msleep() instead.

Fixes: c9e563cae19e ("ixgbe: add support for devlink reload")
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@xxxxxxxxx>
Signed-off-by: Linkui Xiao <xiaolinkui@xxxxxxxxxx>
---
v1:https://lore.kernel.org/all/20260914092626.263886-1-xiaolinkui@xxxxxxx/

v2:
  - Reworded the commit message: mdelay() does not mask interrupts or
    disable preemption, and the ~10 s window is below the soft lockup /
    RCU stall thresholds.  State the actual rationale instead.
  - Split the macro rename into a separate patch.
  - The mdelay() -> msleep() change itself is unchanged, so the
    Reviewed-by tag is kept.

 drivers/net/ethernet/intel/ixgbe/devlink/devlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/devlink/devlink.c b/drivers/net/ethernet/intel/ixgbe/devlink/devlink.c
index cf8908b82f8a..781f13240a0d 100644
--- a/drivers/net/ethernet/intel/ixgbe/devlink/devlink.c
+++ b/drivers/net/ethernet/intel/ixgbe/devlink/devlink.c
@@ -460,7 +460,7 @@ static int ixgbe_devlink_reload_empr_finish(struct devlink *devlink,
 		 * may be not cleared yet, so begin the loop with the delay
 		 * in order to not check the not updated register.
 		 */
-		mdelay(500);
+		msleep(500);
 
 		fwsm = IXGBE_READ_REG(hw, IXGBE_FWSM(hw));
 
-- 
2.25.1