net/tg3: resolve deadlock in tg3_reset_task() during EEH

During EEH error injection testing, a deadlock was encountered in the tg3
driver when tg3_io_error_detected() was attempting to cancel outstanding
reset tasks:

crash> foreach UN bt
...
PID: 159 TASK: c0000000067c6000 CPU: 8 COMMAND: "eehd"
...
#5 [c00000000681f990] __cancel_work_timer at c00000000019fd18
#6 [c00000000681fa30] tg3_io_error_detected at c00800000295f098 [tg3]
#7 [c00000000681faf0] eeh_report_error at c00000000004e25c
...

PID: 290 TASK: c000000036e5f800 CPU: 6 COMMAND: "kworker/6:1"
...
#4 [c00000003721fbc0] rtnl_lock at c000000000c940d8
#5 [c00000003721fbe0] tg3_reset_task at c008000002969358 [tg3]
#6 [c00000003721fc60] process_one_work at c00000000019e5c4
...

PID: 296 TASK: c000000037a65800 CPU: 21 COMMAND: "kworker/21:1"
...
#4 [c000000037247bc0] rtnl_lock at c000000000c940d8
#5 [c000000037247be0] tg3_reset_task at c008000002969358 [tg3]
#6 [c000000037247c60] process_one_work at c00000000019e5c4
...

PID: 655 TASK: c000000036f49000 CPU: 16 COMMAND: "kworker/16:2"
...:1

#4 [c0000000373ebbc0] rtnl_lock at c000000000c940d8
#5 [c0000000373ebbe0] tg3_reset_task at c008000002969358 [tg3]
#6 [c0000000373ebc60] process_one_work at c00000000019e5c4
...

Code inspection shows that both tg3_io_error_detected() and
tg3_reset_task() attempt to acquire the RTNL lock at the beginning of
their code blocks. If tg3_reset_task() should happen to execute between
the times when tg3_io_error_deteced() acquires the RTNL lock and
tg3_reset_task_cancel() is called, a deadlock will occur.

Moving tg3_reset_task_cancel() call earlier within the code block, prior
to acquiring RTNL, prevents this from happening, but also exposes another
deadlock issue where tg3_reset_task() may execute AFTER
tg3_io_error_detected() has executed:

crash> foreach UN bt
PID: 159 TASK: c0000000067d2000 CPU: 9 COMMAND: "eehd"
...
#4 [c000000006867a60] rtnl_lock at c000000000c940d8
#5 [c000000006867a80] tg3_io_slot_reset at c0080000026c2ea8 [tg3]
#6 [c000000006867b00] eeh_report_reset at c00000000004de88
...
PID: 363 TASK: c000000037564000 CPU: 6 COMMAND: "kworker/6:1"
...
#3 [c000000036c1bb70] msleep at c000000000259e6c
#4 [c000000036c1bba0] napi_disable at c000000000c6b848
#5 [c000000036c1bbe0] tg3_reset_task at c0080000026d942c [tg3]
#6 [c000000036c1bc60] process_one_work at c00000000019e5c4
...

This issue can be avoided by aborting tg3_reset_task() if EEH error
recovery is already in progress.

Fixes: db84bf43ef23 ("tg3: tg3_reset_task() needs to use rtnl_lock to synchronize")
Signed-off-by: David Christensen <[e-mail]>
Reviewed-by: Pavan Chebbi <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/broadcom/tg3.c

···
 	rtnl_lock();
 	tg3_full_lock(tp, 0);
 
-	if (!netif_running(tp->dev)) {
+	if (tp->pcierr_recovery || !netif_running(tp->dev)) {
 		tg3_flag_clear(tp, RESET_TASK_PENDING);
 		tg3_full_unlock(tp);
 		rtnl_unlock();
···
 
 	netdev_info(netdev, "PCI I/O error detected\n");
 
+	/* Want to make sure that the reset task doesn't run */
+	tg3_reset_task_cancel(tp);
+
 	rtnl_lock();
 
 	/* Could be second call or maybe we don't have netdev yet */
···
 	tg3_netif_stop(tp);
 
 	tg3_timer_stop(tp);
-
-	/* Want to make sure that the reset task doesn't run */
-	tg3_reset_task_cancel(tp);
 
 	netif_device_detach(netdev);