linux-kernel - [PATCH RFC 5/5] rcuwait: Replace rcu_assign_pointer() with WRITE

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Message-Id: <20190221054942.132388-6-joel@joelfernandes.org>
Date:   Thu, 21 Feb 2019 00:49:42 -0500
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Christian Brauner <christian@...uner.io>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Ahern <dsahern@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Ido Schimmel <idosch@...lanox.com>,
        Ingo Molnar <mingo@...hat.com>,
        intel-wired-lan@...ts.osuosl.org (moderated list:INTEL ETHERNET DRIVERS),
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Josh Triplett <josh@...htriplett.org>, keescook@...omium.org,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        netdev@...r.kernel.org, "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>, rcu@...r.kernel.org,
        Song Liu <songliubraving@...com>,
        Steven Rostedt <rostedt@...dmis.org>,
        xdp-newbies@...r.kernel.org, Yonghong Song <yhs@...com>
Subject: [PATCH RFC 5/5] rcuwait: Replace rcu_assign_pointer() with WRITE_ONCE

This suppresses a sparse error generated due to the recently added
rcu_assign_pointer sparse check below. It seems WRITE_ONCE should be
sufficient here.

>> kernel//locking/percpu-rwsem.c:162:9: sparse: error: incompatible
types in comparison expression (different address spaces)

Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
 include/linux/rcuwait.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/rcuwait.h b/include/linux/rcuwait.h
index 90bfa3279a01..9e5b4760e6c2 100644
--- a/include/linux/rcuwait.h
+++ b/include/linux/rcuwait.h
@@ -44,7 +44,7 @@ extern void rcuwait_wake_up(struct rcuwait *w);
 	 */                                                             \
 	WARN_ON(current->exit_state);                                   \
 									\
-	rcu_assign_pointer((w)->task, current);				\
+	WRITE_ONCE((w)->task, current);					\
 	for (;;) {							\
 		/*							\
 		 * Implicit barrier (A) pairs with (B) in		\
-- 
2.21.0.rc0.258.g878e2cd30e-goog