[Intel-wired-lan] [PATCH] i40e: avoid spin loop in i40e_asq_send_command()
Caleb Sander
csander at purestorage.com
Fri Oct 1 15:50:06 UTC 2021
Previously, the kernel could spend up to 250 ms waiting for a command to
be submitted to an admin queue. This function is also called in a loop,
e.g., in i40e_get_module_eeprom() (through i40e_aq_get_phy_register()),
so the time spent in the kernel may be even higher. We observed
scheduling delays of over 2 seconds in production,
with stacktraces pointing to this code as the culprit.
Add a call to cond_resched() so the loop can yield the CPU.
Also compute the total time using the jiffies counter
instead of assuming udelay() waits the precise time interval requested.
Signed-off-by: Caleb Sander <csander at purestorage.com>
Reviewed-by: Joern Engel <joern at purestorage.com>
---
drivers/net/ethernet/intel/i40e/i40e_adminq.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/intel/i40e/i40e_adminq.c b/drivers/net/ethernet/intel/i40e/i40e_adminq.c
index 593912b17..f1fcb867a 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_adminq.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_adminq.c
@@ -902,7 +902,7 @@ i40e_status i40e_asq_send_command(struct i40e_hw *hw,
* we need to wait for desc write back
*/
if (!details->async && !details->postpone) {
- u32 total_delay = 0;
+ unsigned long timeout_end = jiffies + usecs_to_jiffies(hw->aq.asq_cmd_timeout);
do {
/* AQ designers suggest use of head for better
@@ -910,9 +910,9 @@ i40e_status i40e_asq_send_command(struct i40e_hw *hw,
*/
if (i40e_asq_done(hw))
break;
+ cond_resched();
udelay(50);
- total_delay += 50;
- } while (total_delay < hw->aq.asq_cmd_timeout);
+ } while (time_before(jiffies, timeout_end));
}
/* if ready, copy the desc back to temp */
--
2.17.1
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