sfc: Do not use efx_process_channel_now() in online self-test

During self-tests we use efx_process_channel_now() to handle
completion and other events synchronously.  This disables interrupts
and NAPI processing for the channel in question, but it may still be
interrupted by another channel.  A single socket may receive packets
from multiple net devices or even multiple channels of the same net
device, so this can result in deadlock on a socket lock.

Receiving packets in process context will also result in incorrect
classification by the network cgroup classifier.

Therefore, we must only use efx_process_channel_now() in the offline
loopback tests (which never deliver packets up the stack) and not for
the online interrupt and event tests.

For the interrupt test, there is no reason to process events.  We
only care that an interrupt is raised.

For the event test, we want to know whether events have been received,
and there may be many events ahead of the one we inject.  Therefore
remove efx_channel::magic_count and instead test whether
efx_channel::eventq_read_ptr advances.  This is currently an event
queue index and might wrap around to exactly the same value, resulting
in a false negative.  Therefore move the masking to efx_event() and
efx_nic_eventq_read_ack() so that it cannot wrap within the time of
the test.

The event test also tries to diagnose failures by checking whether an
event was delivered without causing an interrupt.  Add and use a
helper function that only does this.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

1 files changed, 4 insertions, 19 deletions

diff --git a/drivers/net/sfc/selftest.c b/drivers/net/sfc/selftest.c
index 845808408924..50ad3bcaf68a 100644
--- a/drivers/net/sfc/selftest.c
+++ b/drivers/net/sfc/selftest.c
@@ -131,8 +131,6 @@ static int efx_test_chip(struct efx_nic *efx, struct efx_self_tests *tests)
 static int efx_test_interrupts(struct efx_nic *efx,
 			       struct efx_self_tests *tests)
 {
-	struct efx_channel *channel;
-
 	netif_dbg(efx, drv, efx->net_dev, "testing interrupts\n");
 	tests->interrupt = -1;
 
@@ -140,15 +138,6 @@ static int efx_test_interrupts(struct efx_nic *efx,
 	efx->last_irq_cpu = -1;
 	smp_wmb();
 
-	/* ACK each interrupting event queue. Receiving an interrupt due to
-	 * traffic before a test event is raised is considered a pass */
-	efx_for_each_channel(channel, efx) {
-		if (channel->work_pending)
-			efx_process_channel_now(channel);
-		if (efx->last_irq_cpu >= 0)
-			goto success;
-	}
-
 	efx_nic_generate_interrupt(efx);
 
 	/* Wait for arrival of test interrupt. */
@@ -173,13 +162,13 @@ static int efx_test_eventq_irq(struct efx_channel *channel,
 			       struct efx_self_tests *tests)
 {
 	struct efx_nic *efx = channel->efx;
-	unsigned int magic_count, count;
+	unsigned int read_ptr, count;
 
 	tests->eventq_dma[channel->channel] = -1;
 	tests->eventq_int[channel->channel] = -1;
 	tests->eventq_poll[channel->channel] = -1;
 
-	magic_count = channel->magic_count;
+	read_ptr = channel->eventq_read_ptr;
 	channel->efx->last_irq_cpu = -1;
 	smp_wmb();
 
@@ -190,10 +179,7 @@ static int efx_test_eventq_irq(struct efx_channel *channel,
 	do {
 		schedule_timeout_uninterruptible(HZ / 100);
 
-		if (channel->work_pending)
-			efx_process_channel_now(channel);
-
-		if (channel->magic_count != magic_count)
+		if (ACCESS_ONCE(channel->eventq_read_ptr) != read_ptr)
 			goto eventq_ok;
 	} while (++count < 2);
 
@@ -211,8 +197,7 @@ static int efx_test_eventq_irq(struct efx_channel *channel,
 	}
 
 	/* Check to see if event was received even if interrupt wasn't */
-	efx_process_channel_now(channel);
-	if (channel->magic_count != magic_count) {
+	if (efx_nic_event_present(channel)) {
 		netif_err(efx, drv, efx->net_dev,
 			  "channel %d event was generated, but "
 			  "failed to trigger an interrupt\n", channel->channel);