| Message ID | 20250123162045.INxxt33y@linutronix.de (mailing list archive) |
|---|---|
| State | Awaiting Upstream |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] xfrm: Don't disable preemption while looking up cache state. | expand |
On Thu, Jan 23, 2025 at 05:20:45PM +0100, Sebastian Sewior wrote: > For the state cache lookup xfrm_input_state_lookup() first disables > preemption, to remain on the CPU and then retrieves a per-CPU pointer. > Within the preempt-disable section it also acquires > netns_xfrm::xfrm_state_lock, a spinlock_t. This lock must not be > acquired with explicit disabled preemption (such as by get_cpu()) > because this lock becomes a sleeping lock on PREEMPT_RT. > > To remain on the same CPU is just an optimisation for the CPU local > lookup. The actual modification of the per-CPU variable happens with > netns_xfrm::xfrm_state_lock acquired. > > Remove get_cpu() and use the state_cache_input on the current CPU. > > Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com> > Closes: https://lore.kernel.org/all/CAADnVQKkCLaj=roayH=Mjiiqz_svdf1tsC3OE4EC0E=mAD+L1A@mail.gmail.com/ > Fixes: 81a331a0e72dd ("xfrm: Add an inbound percpu state cache.") > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Applied to the ipsec tree, thanks a lot Sebastian!
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c index 67ca7ac955a37..66b108a5b87d4 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -1116,9 +1116,8 @@ struct xfrm_state *xfrm_input_state_lookup(struct net *net, u32 mark, { struct hlist_head *state_cache_input; struct xfrm_state *x = NULL; - int cpu = get_cpu(); - state_cache_input = per_cpu_ptr(net->xfrm.state_cache_input, cpu); + state_cache_input = raw_cpu_ptr(net->xfrm.state_cache_input); rcu_read_lock(); hlist_for_each_entry_rcu(x, state_cache_input, state_cache_input) { @@ -1150,7 +1149,6 @@ struct xfrm_state *xfrm_input_state_lookup(struct net *net, u32 mark, out: rcu_read_unlock(); - put_cpu(); return x; } EXPORT_SYMBOL(xfrm_input_state_lookup);
For the state cache lookup xfrm_input_state_lookup() first disables preemption, to remain on the CPU and then retrieves a per-CPU pointer. Within the preempt-disable section it also acquires netns_xfrm::xfrm_state_lock, a spinlock_t. This lock must not be acquired with explicit disabled preemption (such as by get_cpu()) because this lock becomes a sleeping lock on PREEMPT_RT. To remain on the same CPU is just an optimisation for the CPU local lookup. The actual modification of the per-CPU variable happens with netns_xfrm::xfrm_state_lock acquired. Remove get_cpu() and use the state_cache_input on the current CPU. Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com> Closes: https://lore.kernel.org/all/CAADnVQKkCLaj=roayH=Mjiiqz_svdf1tsC3OE4EC0E=mAD+L1A@mail.gmail.com/ Fixes: 81a331a0e72dd ("xfrm: Add an inbound percpu state cache.") Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- net/xfrm/xfrm_state.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)