svc_xprt_enqueue() disables preemption via get_cpu() and then asks for a
pool of a specific CPU (current) via svc_pool_for_cpu().
With disabled preemption it acquires svc_pool::sp_lock, a spinlock_t,
which is a sleeping lock on PREEMPT_RT and can't be acquired with
disabled preemption.
Disabling preemption is not required here. The pool is protected with a
lock so the following list access is safe even cross-CPU. The following
iteration through svc_pool::sp_all_threads is under RCU-readlock and
remaining operations within the loop are atomic and do not rely on
disabled-preemption.
Use raw_smp_processor_id() as the argument for the requested CPU in
svc_pool_for_cpu().
Reported-by: Mike Galbraith <umgwanakikbuti@xxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
net/sunrpc/svc_xprt.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index 5b59e2103526e..79965deec5b12 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -448,7 +448,6 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
{
struct svc_pool *pool;
struct svc_rqst *rqstp = NULL;
- int cpu;
if (!svc_xprt_ready(xprt))
return;
@@ -461,8 +460,7 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
if (test_and_set_bit(XPT_BUSY, &xprt->xpt_flags))
return;
- cpu = get_cpu();
- pool = svc_pool_for_cpu(xprt->xpt_server, cpu);
+ pool = svc_pool_for_cpu(xprt->xpt_server, raw_smp_processor_id());
atomic_long_inc(&pool->sp_stats.packets);
@@ -485,7 +483,6 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
rqstp = NULL;
out_unlock:
rcu_read_unlock();
- put_cpu();
trace_svc_xprt_enqueue(xprt, rqstp);
}
EXPORT_SYMBOL_GPL(svc_xprt_enqueue);
--
2.36.0
