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

From: Prakash Sangappa
Date: Mon Apr 25 2022 - 15:39:14 EST




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

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
>