On Mon, Dec 21, 2015 at 11:15 AM, Richard Cochran <richardcoch...@gmail.com> wrote: > On Sun, Dec 20, 2015 at 11:46:30PM +0200, Saeed Mahameed wrote: >> +/* Should run once every mlx5e_tstamp->overflow_period */ >> +static void mlx5e_timestamp_overflow(struct work_struct *work) >> +{ >> + struct delayed_work *dwork = to_delayed_work(work); >> + struct mlx5e_tstamp *tstamp = container_of(dwork, struct mlx5e_tstamp, >> overflow_work); >> + unsigned long flags; >> + >> + write_lock_irqsave(&tstamp->lock, flags); >> + timecounter_read(&tstamp->clock); >> + if (tstamp->overflow_period) >> + schedule_delayed_work(&tstamp->overflow_work, >> tstamp->overflow_period); > > You don't need this test, and the call to schedule_delayed_work can be > outside of the lock. >
think of a case where: CPU1: is just about to call "schedule_delayed_work(&tstamp->overflow_work, tstamp->overflow_period);" CPU2: cancel_delayed_work In this case cancel_dalyed_work_sync (CPU2) will wait for CPU1 to complete but CPU1 will re-arm the work, and we will be left with tstamp->overflow_work running forever. >> + write_unlock_irqrestore(&tstamp->lock, flags); >> +} > >> +void mlx5e_timestamp_cleanup(struct mlx5e_priv *priv) >> +{ >> + struct mlx5e_tstamp *tstamp = &priv->tstamp; >> + >> + if (!MLX5_CAP_GEN(priv->mdev, device_frequency_khz)) >> + return; >> + >> + write_lock(&tstamp->lock); >> + tstamp->overflow_period = 0; /* Signal overflow_check to stop */ >> + write_unlock(&tstamp->lock); > > This is unnecessary because > >> + >> + cancel_delayed_work_sync(&tstamp->overflow_work); > > this will block until the work is cancelled. > see my previous comment it sure will block but without the protected signal " tstamp->overflow_period = 0;" the work can reschedule itself. >> +} > > Thanks, > Richard > > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html