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authorPaolo Abeni <pabeni@redhat.com>2021-04-09 17:24:17 +0200
committerJakub Kicinski <kuba@kernel.org>2021-04-09 12:50:31 -0700
commit27f0ad71699de41bae013c367b95a6b319cc46a9 (patch)
treef74e446319f81d7d42410f8b06b5a56235903c53 /net
parentcd7e963d2f0875789ddb5c3746b628716bd0a8c9 (diff)
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.c3
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;
}