netdev - [PATCH net-next] net: fix napi

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Message-ID: <20221117092641.3319176-1-edumazet@google.com>
Date:   Thu, 17 Nov 2022 09:26:41 +0000
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Eric Dumazet <edumazet@...gle.com>,
        kernel test robot <lkp@...el.com>,
        Dan Carpenter <error27@...il.com>
Subject: [PATCH net-next] net: fix napi_disable() logic error

Dan reported a new warning after my recent patch:

New smatch warnings:
net/core/dev.c:6409 napi_disable() error: uninitialized symbol 'new'.

Indeed, we must first wait for STATE_SCHED and STATE_NPSVC to be cleared,
to make sure @new variable has been initialized properly.

Fixes: 4ffa1d1c6842 ("net: adopt try_cmpxchg() in napi_{enable|disable}()")
Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Dan Carpenter <error27@...il.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/dev.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index d0fb4af9a12611c7f82798a700205604730e4d10..7627c475d991bfeb7138e0868d423e654d46f036 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6399,9 +6399,9 @@ void napi_disable(struct napi_struct *n)
 
 	val = READ_ONCE(n->state);
 	do {
-		if (val & (NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC)) {
+		while (val & (NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC)) {
 			usleep_range(20, 200);
-			continue;
+			val = READ_ONCE(n->state);
 		}
 
 		new = val | NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC;
-- 
2.38.1.431.g37b22c650d-goog