linux-kernel - [PATCH] MIPS: Use rcu to lookup a task in mipsmt_sys_sched

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Message-Id: <20200831201402.2837-1-dave@stgolabs.net>
Date:   Mon, 31 Aug 2020 13:14:02 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     tsbogend@...ha.franken.de
Cc:     oleg@...hat.com, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org, dave@...olabs.net,
        Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH] MIPS: Use rcu to lookup a task in mipsmt_sys_sched_setaffinity()

The call simply looks up the corresponding task (without iterating
the tasklist), which is safe under rcu instead of the tasklist_lock.
In addition, the setaffinity counter part already does this.

Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
---
 arch/mips/kernel/mips-mt-fpaff.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kernel/mips-mt-fpaff.c b/arch/mips/kernel/mips-mt-fpaff.c
index 1a08428eedcf..6c590ef27648 100644
--- a/arch/mips/kernel/mips-mt-fpaff.c
+++ b/arch/mips/kernel/mips-mt-fpaff.c
@@ -167,7 +167,7 @@ asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
 		return -EINVAL;
 
 	get_online_cpus();
-	read_lock(&tasklist_lock);
+	rcu_read_lock();
 
 	retval = -ESRCH;
 	p = find_process_by_pid(pid);
@@ -181,7 +181,7 @@ asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
 	cpumask_and(&mask, &allowed, cpu_active_mask);
 
 out_unlock:
-	read_unlock(&tasklist_lock);
+	rcu_read_unlock();
 	put_online_cpus();
 	if (retval)
 		return retval;
-- 
2.26.2