linux-kernel - [PATCH v3 5/5] pid: use pid_has_task() in pidfd

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Date:   Thu, 17 Oct 2019 12:18:32 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     oleg@...hat.com, linux-kernel@...r.kernel.org
Cc:     aarcange@...hat.com, akpm@...ux-foundation.org,
        christian@...lner.me, cyphar@...har.com, elena.reshetova@...el.com,
        guro@...com, jannh@...gle.com, ldv@...linux.org,
        linux-api@...r.kernel.org, linux-kselftest@...r.kernel.org,
        mhocko@...e.com, mingo@...nel.org, peterz@...radead.org,
        shuah@...nel.org, tglx@...utronix.de, viro@...iv.linux.org.uk,
        Christian Brauner <christian.brauner@...ntu.com>
Subject: [PATCH v3 5/5] pid: use pid_has_task() in pidfd_open()

Use the new pid_has_task() helper in pidfd_open(). This simplifies the
code and avoids taking rcu_read_{lock,unlock}() and leads to overall
nicer code.

Signed-off-by: Christian Brauner <christian.brauner@...ntu.com>
Reviewed-by: Oleg Nesterov <oleg@...hat.com>
---
/* pidfd selftests */
passed

/* v1 */
patch not present

/* v2 */
Link: https://lore.kernel.org/r/20191016153606.2326-5-christian.brauner@ubuntu.com
patch introduced

/* v3 */
- Oleg Nesterov <oleg@...hat.com>:
  - s/task_alive/pid_has_task/
---
 kernel/pid.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/kernel/pid.c b/kernel/pid.c
index 124d40b239b1..7b5f6c963d72 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -497,7 +497,7 @@ static int pidfd_create(struct pid *pid)
  */
 SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags)
 {
-	int fd, ret;
+	int fd;
 	struct pid *p;
 
 	if (flags)
@@ -510,13 +510,11 @@ SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags)
 	if (!p)
 		return -ESRCH;
 
-	ret = 0;
-	rcu_read_lock();
-	if (!pid_task(p, PIDTYPE_TGID))
-		ret = -EINVAL;
-	rcu_read_unlock();
+	if (pid_has_task(p, PIDTYPE_TGID))
+		fd = pidfd_create(p);
+	else
+		fd = -EINVAL;
 
-	fd = ret ?: pidfd_create(p);
 	put_pid(p);
 	return fd;
 }
-- 
2.23.0