netdev - [PATCH net 01/11] netpoll: do not test NAPI_STATE_SCHED in poll_one

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Date:   Thu, 27 Sep 2018 09:31:51 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Michael Chan <michael.chan@...adcom.com>,
        Aviad Krawczyk <aviad.krawczyk@...wei.com>,
        Song Liu <songliubraving@...com>,
        Douglas Miller <dougmill@...ux.vnet.ibm.com>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Harish Patil <harish.patil@...ium.com>,
        Manish Chopra <manish.chopra@...ium.com>,
        Netanel Belgazal <netanel@...zon.com>,
        Solarflare linux maintainers <linux-net-drivers@...arflare.com>,
        Thomas Falcon <tlfalcon@...ux.vnet.ibm.com>
Subject: [PATCH net 01/11] netpoll: do not test NAPI_STATE_SCHED in poll_one_napi()

Since we do no longer require NAPI drivers to provide
an ndo_poll_controller(), napi_schedule() has not been done
before poll_one_napi() invocation.

So testing NAPI_STATE_SCHED is likely to cause early returns.

While we are at it, remove outdated comment.

Note to future bisections : This change might surface prior
bugs in drivers. See commit 73f21c653f93 ("bnxt_en: Fix TX
timeout during netpoll.") for one occurrence.

Fixes: ac3d9dd034e5 ("netpoll: make ndo_poll_controller() optional")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Tested-by: Song Liu <songliubraving@...com>
Cc: Michael Chan <michael.chan@...adcom.com>
---
 net/core/netpoll.c | 20 +-------------------
 1 file changed, 1 insertion(+), 19 deletions(-)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 3219a2932463096566ce8ff336ecdf699422dd65..3ae899805f8b674b4ffb7d791330f836d38eff7d 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -135,27 +135,9 @@ static void queue_process(struct work_struct *work)
 	}
 }
 
-/*
- * Check whether delayed processing was scheduled for our NIC. If so,
- * we attempt to grab the poll lock and use ->poll() to pump the card.
- * If this fails, either we've recursed in ->poll() or it's already
- * running on another CPU.
- *
- * Note: we don't mask interrupts with this lock because we're using
- * trylock here and interrupts are already disabled in the softirq
- * case. Further, we test the poll_owner to avoid recursion on UP
- * systems where the lock doesn't exist.
- */
 static void poll_one_napi(struct napi_struct *napi)
 {
-	int work = 0;
-
-	/* net_rx_action's ->poll() invocations and our's are
-	 * synchronized by this test which is only made while
-	 * holding the napi->poll_lock.
-	 */
-	if (!test_bit(NAPI_STATE_SCHED, &napi->state))
-		return;
+	int work;
 
 	/* If we set this bit but see that it has already been set,
 	 * that indicates that napi has been disabled and we need
-- 
2.19.0.605.g01d371f741-goog