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

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Message-ID: <8603345D-9AAD-43FF-B1DF-941BDA799DF5@oracle.com>
Date:   Mon, 25 Apr 2022 19:38:44 +0000
From:   Prakash Sangappa <prakash.sangappa@...cle.com>
To:     LKML <linux-kernel@...r.kernel.org>
CC:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] ipc: Update semtimedop() to use hrtimer



> On Apr 18, 2022, at 6:51 PM, Prakash Sangappa <prakash.sangappa@...cle.com> wrote:
> 
> 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>

Can I get a review of this patch?
Note this patch has been added to Andrew's mm tree.


> ---
> ipc/sem.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/ipc/sem.c b/ipc/sem.c
> index 0dbdb98..6cd1a1b8 100644
> --- a/ipc/sem.c
> +++ b/ipc/sem.c
> @@ -1995,7 +1995,10 @@ 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;
> +	int timed_out = 0;
> +	struct timespec64 end_time;
> 
> 	if (nsops < 1 || semid < 0)
> 		return -EINVAL;
> @@ -2008,7 +2011,9 @@ long __do_semtimedop(int semid, struct sembuf *sops,
> 			error = -EINVAL;
> 			goto out;
> 		}
> -		jiffies_left = timespec64_to_jiffies(timeout);
> +		ktime_get_ts64(&end_time);
> +		end_time = timespec64_add_safe(end_time, *timeout);
> +		expires = timespec64_to_ktime(end_time);
> 	}
> 
> 
> @@ -2167,7 +2172,9 @@ long __do_semtimedop(int semid, struct sembuf *sops,
> 		rcu_read_unlock();
> 
> 		if (timeout)
> -			jiffies_left = schedule_timeout(jiffies_left);
> +			timed_out = !schedule_hrtimeout_range(&expires,
> +						current->timer_slack_ns,
> +						HRTIMER_MODE_ABS);
> 		else
> 			schedule();
> 
> @@ -2210,7 +2217,7 @@ 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 (timeout && timed_out)
> 			error = -EAGAIN;
> 	} while (error == -EINTR && !signal_pending(current)); /* spurious */
> 
> -- 
> 2.7.4
>