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net: ena: fix rare uncompleted admin command false alarm 

The current flow to detect admin completion is:
while (command_not_completed) {
	if (timeout)
		error

	check_for_completion()
		sleep()
   }
So in case the sleep took more than the timeout
(in case the thread/workqueue was not scheduled due to higher priority
task or prolonged VMexit), the driver can detect a stall even if
the completion is present.

The fix changes the order of this function to first check for
completion and only after that check if the timeout expired.

Fixes: 1738cd3ed3 ("Add a driver for Amazon Elastic Network Adapters (ENA)")
Signed-off-by: Netanel Belgazal <netanel@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Netanel Belgazal 2017-06-11 15:42:43 +03:00 committed by David S. Miller
parent b87fa0fafe
commit a77c1aafcc
1 changed files with 11 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
drivers/net/ethernet/amazon/ena/ena_com.c
View File

@ -508,15 +508,20 @@ static int ena_com_comp_status_to_errno(u8 comp_status)
static int ena_com_wait_and_process_admin_cq_polling(struct ena_comp_ctx *comp_ctx,
struct ena_com_admin_queue *admin_queue)
{
unsigned long flags;
u32 start_time;
unsigned long flags, timeout;
int ret;
start_time = ((u32)jiffies_to_usecs(jiffies));
timeout = jiffies + ADMIN_CMD_TIMEOUT_US;
while (comp_ctx->status == ENA_CMD_SUBMITTED) {
if ((((u32)jiffies_to_usecs(jiffies)) - start_time) >
ADMIN_CMD_TIMEOUT_US) {
while (1) {
spin_lock_irqsave(&admin_queue->q_lock, flags);
ena_com_handle_admin_completion(admin_queue);
spin_unlock_irqrestore(&admin_queue->q_lock, flags);
if (comp_ctx->status != ENA_CMD_SUBMITTED)
break;
if (time_is_before_jiffies(timeout)) {
pr_err("Wait for completion (polling) timeout\n");
/* ENA didn't have any completion */
spin_lock_irqsave(&admin_queue->q_lock, flags);
@ -528,10 +533,6 @@ static int ena_com_wait_and_process_admin_cq_polling(struct ena_comp_ctx *comp_c
goto err;
}
spin_lock_irqsave(&admin_queue->q_lock, flags);
ena_com_handle_admin_completion(admin_queue);
spin_unlock_irqrestore(&admin_queue->q_lock, flags);
msleep(100);
}