linux-kernel - [PATCH v4] ipc: Update semtimedop() to use hrtimer

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Date:   Thu, 28 Apr 2022 16:18:01 -0700
From:   Prakash Sangappa <prakash.sangappa@...cle.com>
To:     linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, akpm@...ux-foundation.org,
        peterz@...radead.org, dave@...olabs.net, manfred@...orfullife.com,
        Prakash Sangappa <prakash.sangappa@...cle.com>
Subject: [PATCH v4] ipc: Update semtimedop() to use hrtimer

semtimedop() should be converted to use hrtimer like it has been done
for most of the system calls with timeouts. This system call already
takes a struct timespec as an argument and can therefore provide finer
granularity timed wait.

Signed-off-by: Prakash Sangappa <prakash.sangappa@...cle.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Davidlohr Bueso <dave@...olabs.net>
---
v1->v2:
  - Use timespec64_valid() to validate timeout
     and other changes as suggested by Thomas Gleixner
v2->v3: Added Reviewed by tag (Thomas)
v3->v4: Added Reviewed by (Davidlohr)

 ipc/sem.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/ipc/sem.c b/ipc/sem.c
index 0dbdb98..44b65b6 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1995,7 +1995,9 @@ long __do_semtimedop(int semid, struct sembuf *sops,
 	int max, locknum;
 	bool undos = false, alter = false, dupsop = false;
 	struct sem_queue queue;
-	unsigned long dup = 0, jiffies_left = 0;
+	unsigned long dup = 0;
+	ktime_t expires, *exp = NULL;
+	bool timed_out = false;
 
 	if (nsops < 1 || semid < 0)
 		return -EINVAL;
@@ -2003,12 +2005,11 @@ long __do_semtimedop(int semid, struct sembuf *sops,
 		return -E2BIG;
 
 	if (timeout) {
-		if (timeout->tv_sec < 0 || timeout->tv_nsec < 0 ||
-			timeout->tv_nsec >= 1000000000L) {
-			error = -EINVAL;
-			goto out;
-		}
-		jiffies_left = timespec64_to_jiffies(timeout);
+		if (!timespec64_valid(timeout))
+			return -EINVAL;
+		expires = ktime_add_safe(ktime_get(),
+				timespec64_to_ktime(*timeout));
+		exp = &expires;
 	}
 
 
@@ -2166,10 +2167,8 @@ long __do_semtimedop(int semid, struct sembuf *sops,
 		sem_unlock(sma, locknum);
 		rcu_read_unlock();
 
-		if (timeout)
-			jiffies_left = schedule_timeout(jiffies_left);
-		else
-			schedule();
+		timed_out = !schedule_hrtimeout_range(exp,
+				current->timer_slack_ns, HRTIMER_MODE_ABS);
 
 		/*
 		 * fastpath: the semop has completed, either successfully or
@@ -2210,7 +2209,7 @@ long __do_semtimedop(int semid, struct sembuf *sops,
 		/*
 		 * If an interrupt occurred we have to clean up the queue.
 		 */
-		if (timeout && jiffies_left == 0)
+		if (timed_out)
 			error = -EAGAIN;
 	} while (error == -EINTR && !signal_pending(current)); /* spurious */
 
-- 
2.7.4