* [PATCH net-next v2] net: make napi_disable() symmetric with enable
@ 2021-09-24 20:24 Jakub Kicinski
2021-09-27 11:30 ` patchwork-bot+netdevbpf
0 siblings, 1 reply; 2+ messages in thread
From: Jakub Kicinski @ 2021-09-24 20:24 UTC (permalink / raw)
To: davem; +Cc: netdev, eric.dumazet, weiwan, xuanzhuo, Jakub Kicinski
Commit 3765996e4f0b ("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>
---
net/core/dev.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 62ddd7d6e00d..fa989ab63f29 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -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);
--
2.31.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH net-next v2] net: make napi_disable() symmetric with enable
2021-09-24 20:24 [PATCH net-next v2] net: make napi_disable() symmetric with enable Jakub Kicinski
@ 2021-09-27 11:30 ` patchwork-bot+netdevbpf
0 siblings, 0 replies; 2+ messages in thread
From: patchwork-bot+netdevbpf @ 2021-09-27 11:30 UTC (permalink / raw)
To: Jakub Kicinski; +Cc: davem, netdev, eric.dumazet, weiwan, xuanzhuo
Hello:
This patch was applied to netdev/net-next.git (refs/heads/master):
On Fri, 24 Sep 2021 13:24:53 -0700 you wrote:
> Commit 3765996e4f0b ("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.
>
> [...]
Here is the summary with links:
- [net-next,v2] net: make napi_disable() symmetric with enable
https://git.kernel.org/netdev/net-next/c/719c57197010
You are awesome, thank you!
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2021-09-27 11:30 ` patchwork-bot+netdevbpf
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