Commit 586095d3 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Chuck Lever
Browse files

SUNRPC: Don't disable preemption while calling svc_pool_for_cpu(). 



svc_xprt_enqueue() disables preemption via get_cpu() and then asks
for a pool of a specific CPU (current) via svc_pool_for_cpu().
While preemption is disabled, svc_xprt_enqueue() acquires
svc_pool::sp_lock with bottom-halfs disabled, which can sleep on
PREEMPT_RT.

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: default avatarMike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent e9488d5a

net/sunrpc/svc_xprt.c

+1 −4
Original line number Diff line number Diff line
@@ -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);