Commit 719c5719 authored by Jakub Kicinski's avatar Jakub Kicinski Committed by David S. Miller
Browse files

net: make napi_disable() symmetric with enable 



Commit 3765996e ("napi: fix race inside napi_enable") fixed
an ordering bug in napi_enable() and made the napi_enable() diverge
from napi_disable(). The state transitions done on disable are
not symmetric to enable.

There is no known bug in napi_disable() this is just refactoring.

Eric suggests we can also replace msleep(1) with a more opportunistic
usleep_range().

Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 930dfa56

net/core/dev.c

+12 −6
Original line number Diff line number Diff line
@@ -6900,19 +6900,25 @@ EXPORT_SYMBOL(netif_napi_add); 


void napi_disable(struct napi_struct *n)

{

	unsigned long val, new;



	might_sleep();

	set_bit(NAPI_STATE_DISABLE, &n->state);



	while (test_and_set_bit(NAPI_STATE_SCHED, &n->state))

		msleep(1);

	while (test_and_set_bit(NAPI_STATE_NPSVC, &n->state))

		msleep(1);

	do {

		val = READ_ONCE(n->state);

		if (val & (NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC)) {

			usleep_range(20, 200);

			continue;

		}



		new = val | NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC;

		new &= ~(NAPIF_STATE_THREADED | NAPIF_STATE_PREFER_BUSY_POLL);

	} while (cmpxchg(&n->state, val, new) != val);



	hrtimer_cancel(&n->timer);



	clear_bit(NAPI_STATE_PREFER_BUSY_POLL, &n->state);

	clear_bit(NAPI_STATE_DISABLE, &n->state);

	clear_bit(NAPI_STATE_THREADED, &n->state);

}

EXPORT_SYMBOL(napi_disable);