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net: make napi_disable() symmetric with enable

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Commit 3765996e4f ("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: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jakub Kicinski 2021-09-24 13:24:53 -07:00 committed by David S. Miller
parent 930dfa5631
commit 719c571970
1 changed files with 12 additions and 6 deletions
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18
net/core/dev.c
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@ -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);