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netpoll: Use rcu_access_pointer() in netpoll_poll_lock

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The ndev->npinfo pointer in netpoll_poll_lock() is RCU-protected but is
being accessed directly for a NULL check. While no RCU read lock is held
in this context, we should still use proper RCU primitives for
consistency and correctness.

Replace the direct NULL check with rcu_access_pointer(), which is the
appropriate primitive when only checking for NULL without dereferencing
the pointer. This function provides the necessary ordering guarantees
without requiring RCU read-side protection.

Fixes: bea3348eef ("[NET]: Make NAPI polling independent of struct net_device objects.")
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>
Link: https://patch.msgid.link/20241118-netpoll_rcu-v1-2-a1888dcb4a02@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Breno Leitao 2024-11-18 03:15:18 -08:00 committed by Jakub Kicinski
parent c69c5e10ad
commit a57d5a72f8
1 changed files with 1 additions and 1 deletions
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2
include/linux/netpoll.h
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@ -72,7 +72,7 @@ static inline void *netpoll_poll_lock(struct napi_struct *napi)
{ {
struct net_device *dev = napi->dev; struct net_device *dev = napi->dev;
if (dev && dev->npinfo) { if (dev && rcu_access_pointer(dev->npinfo)) {
int owner = smp_processor_id(); int owner = smp_processor_id();
while (cmpxchg(&napi->poll_owner, -1, owner) != -1) while (cmpxchg(&napi->poll_owner, -1, owner) != -1)