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| author | Paolo Abeni <pabeni@redhat.com> | 2021-04-09 17:24:17 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2021-04-09 12:50:31 -0700 |
| commit | 27f0ad71699de41bae013c367b95a6b319cc46a9 (patch) | |
| tree | f74e446319f81d7d42410f8b06b5a56235903c53 /net | |
| parent | cd7e963d2f0875789ddb5c3746b628716bd0a8c9 (diff) | |
| download | linux-27f0ad71699de41bae013c367b95a6b319cc46a9.tar.bz2 | |
net: fix hangup on napi_disable for threaded napi
napi_disable() is subject to an hangup, when the threaded
mode is enabled and the napi is under heavy traffic.
If the relevant napi has been scheduled and the napi_disable()
kicks in before the next napi_threaded_wait() completes - so
that the latter quits due to the napi_disable_pending() condition,
the existing code leaves the NAPI_STATE_SCHED bit set and the
napi_disable() loop waiting for such bit will hang.
This patch addresses the issue by dropping the NAPI_STATE_DISABLE
bit test in napi_thread_wait(). The later napi_threaded_poll()
iteration will take care of clearing the NAPI_STATE_SCHED.
This also addresses a related problem reported by Jakub:
before this patch a napi_disable()/napi_enable() pair killed
the napi thread, effectively disabling the threaded mode.
On the patched kernel napi_disable() simply stops scheduling
the relevant thread.
v1 -> v2:
- let the main napi_thread_poll() loop clear the SCHED bit
Reported-by: Jakub Kicinski <kuba@kernel.org>
Fixes: 29863d41bb6e ("net: implement threaded-able napi poll loop support")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/883923fa22745a9589e8610962b7dc59df09fb1f.1617981844.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/core/dev.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index 0f72ff5d34ba..af8c1ea040b9 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6992,7 +6992,7 @@ static int napi_thread_wait(struct napi_struct *napi) set_current_state(TASK_INTERRUPTIBLE); - while (!kthread_should_stop() && !napi_disable_pending(napi)) { + while (!kthread_should_stop()) { /* Testing SCHED_THREADED bit here to make sure the current * kthread owns this napi and could poll on this napi. * Testing SCHED bit is not enough because SCHED bit might be @@ -7010,6 +7010,7 @@ static int napi_thread_wait(struct napi_struct *napi) set_current_state(TASK_INTERRUPTIBLE); } __set_current_state(TASK_RUNNING); + return -1; } |