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65 lines
1.9 KiB
Diff
65 lines
1.9 KiB
Diff
From git@z Thu Jan 1 00:00:00 1970
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Subject: [PATCH v2] net: make napi_disable() symmetric with enable
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From: Jakub Kicinski <kuba@kernel.org>
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Date: Fri, 24 Sep 2021 13:24:53 -0700
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Message-Id: <20210924202453.1051687-1-kuba@kernel.org>
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To: davem@davemloft.net
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Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com, weiwan@google.com, xuanzhuo@linux.alibaba.com, Jakub Kicinski <kuba@kernel.org>
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List-Id: <netdev.vger.kernel.org>
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MIME-Version: 1.0
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Content-Type: text/plain; charset="utf-8"
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Content-Transfer-Encoding: 7bit
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Commit 3765996e4f0b ("napi: fix race inside napi_enable") fixed
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an ordering bug in napi_enable() and made the napi_enable() diverge
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from napi_disable(). The state transitions done on disable are
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not symmetric to enable.
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There is no known bug in napi_disable() this is just refactoring.
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Eric suggests we can also replace msleep(1) with a more opportunistic
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usleep_range().
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Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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---
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net/core/dev.c | 17 ++++++++++++-----
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1 file changed, 12 insertions(+), 5 deletions(-)
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diff --git a/net/core/dev.c b/net/core/dev.c
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index f24c3a9..f0a556a 100644
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--- a/net/core/dev.c
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+++ b/net/core/dev.c
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@@ -6386,18 +6386,25 @@ EXPORT_SYMBOL(netif_napi_add);
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void napi_disable(struct napi_struct *n)
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{
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+ unsigned long val, new;
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+
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might_sleep();
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set_bit(NAPI_STATE_DISABLE, &n->state);
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- while (test_and_set_bit(NAPI_STATE_SCHED, &n->state))
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- msleep(1);
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- while (test_and_set_bit(NAPI_STATE_NPSVC, &n->state))
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- msleep(1);
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+ do {
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+ val = READ_ONCE(n->state);
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+ if (val & (NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC)) {
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+ usleep_range(20, 200);
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+ continue;
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+ }
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+
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+ new = val | NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC;
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+ new &= ~(NAPIF_STATE_THREADED);
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+ } while (cmpxchg(&n->state, val, new) != val);
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hrtimer_cancel(&n->timer);
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clear_bit(NAPI_STATE_DISABLE, &n->state);
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- clear_bit(NAPI_STATE_THREADED, &n->state);
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}
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EXPORT_SYMBOL(napi_disable);
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--
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2.31.1
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