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01bebc070c
The workqueue based implementation has a few corner cases and typically lower performance than the upstream one Signed-off-by: Felix Fietkau <nbd@nbd.name>
54 lines
2.0 KiB
Diff
54 lines
2.0 KiB
Diff
From: Paolo Abeni <pabeni@redhat.com>
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Date: Fri, 9 Apr 2021 17:24:17 +0200
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Subject: [PATCH] net: fix hangup on napi_disable for threaded napi
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napi_disable() is subject to an hangup, when the threaded
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mode is enabled and the napi is under heavy traffic.
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If the relevant napi has been scheduled and the napi_disable()
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kicks in before the next napi_threaded_wait() completes - so
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that the latter quits due to the napi_disable_pending() condition,
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the existing code leaves the NAPI_STATE_SCHED bit set and the
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napi_disable() loop waiting for such bit will hang.
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This patch addresses the issue by dropping the NAPI_STATE_DISABLE
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bit test in napi_thread_wait(). The later napi_threaded_poll()
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iteration will take care of clearing the NAPI_STATE_SCHED.
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This also addresses a related problem reported by Jakub:
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before this patch a napi_disable()/napi_enable() pair killed
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the napi thread, effectively disabling the threaded mode.
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On the patched kernel napi_disable() simply stops scheduling
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the relevant thread.
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v1 -> v2:
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- let the main napi_thread_poll() loop clear the SCHED bit
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Reported-by: Jakub Kicinski <kuba@kernel.org>
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Fixes: 29863d41bb6e ("net: implement threaded-able napi poll loop support")
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Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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Reviewed-by: Eric Dumazet <edumazet@google.com>
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Link: https://lore.kernel.org/r/883923fa22745a9589e8610962b7dc59df09fb1f.1617981844.git.pabeni@redhat.com
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Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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---
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--- a/net/core/dev.c
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+++ b/net/core/dev.c
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@@ -6518,7 +6518,7 @@ static int napi_thread_wait(struct napi_
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set_current_state(TASK_INTERRUPTIBLE);
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- while (!kthread_should_stop() && !napi_disable_pending(napi)) {
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+ while (!kthread_should_stop()) {
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/* Testing SCHED_THREADED bit here to make sure the current
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* kthread owns this napi and could poll on this napi.
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* Testing SCHED bit is not enough because SCHED bit might be
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@@ -6536,6 +6536,7 @@ static int napi_thread_wait(struct napi_
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set_current_state(TASK_INTERRUPTIBLE);
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}
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__set_current_state(TASK_RUNNING);
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+
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return -1;
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}
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