From mboxrd@z Thu Jan 1 00:00:00 1970 From: Caleb Sander Date: Fri, 1 Oct 2021 09:50:06 -0600 Subject: [Intel-wired-lan] [PATCH] i40e: avoid spin loop in i40e_asq_send_command() Message-ID: <20211001155006.30732-1-csander@purestorage.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: intel-wired-lan@osuosl.org List-ID: 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 Reviewed-by: Joern Engel --- 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