| Message ID | a8994b5dda7599c0d8ce9f66aef40b8587acf691.1404888801.git.viresh.kumar@linaro.org |
|---|---|
| State | New |
| Headers | show |
Hi Viresh, On 09/07/14 07:55, Viresh Kumar wrote: > hrtimer_start*() family never fails to enqueue a hrtimer to a clock-base. The > only special case is when the hrtimer was in past. If it is getting enqueued to > local CPUs's clock-base, we raise a softirq and exit, else we handle that on > next interrupt on remote CPU. > > At several places in the kernel, we try to make sure if hrtimer was added > properly or not by calling hrtimer_active(), like: > > hrtimer_start(timer, expires, mode); > if (hrtimer_active(timer)) { > /* Added successfully */ > } else { > /* Was added in the past */ > } > > As hrtimer_start*() never fails, hrtimer_active() is guaranteed to return '1'. > So, there is no point calling hrtimer_active(). > > This patch updates net core to get this fixed. > > Cc: "David S. Miller" <davem@davemloft.net> > Cc: netdev@vger.kernel.org > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> > --- > net/core/pktgen.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/net/core/pktgen.c b/net/core/pktgen.c > index fc17a9d..f911acd 100644 > --- a/net/core/pktgen.c > +++ b/net/core/pktgen.c > @@ -2186,8 +2186,6 @@ static void spin(struct pktgen_dev *pkt_dev, ktime_t spin_until) > do { > set_current_state(TASK_INTERRUPTIBLE); > hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS); > - if (!hrtimer_active(&t.timer)) > - t.task = NULL; > > if (likely(t.task)) > schedule(); I think this if condition can also be removed. hrtimer_init_sleeper copies the supplied task_struct * to the timer, which in this case is 'current'. The check is likely to be there in case of !active case you removed. > --Chris -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Hi Chris, On 9 July 2014 16:02, Chris Redpath <Chris.Redpath@arm.com> wrote: >> diff --git a/net/core/pktgen.c b/net/core/pktgen.c >> index fc17a9d..f911acd 100644 >> --- a/net/core/pktgen.c >> +++ b/net/core/pktgen.c >> @@ -2186,8 +2186,6 @@ static void spin(struct pktgen_dev *pkt_dev, ktime_t >> spin_until) >> do { >> set_current_state(TASK_INTERRUPTIBLE); >> hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS); >> - if (!hrtimer_active(&t.timer)) >> - t.task = NULL; >> >> if (likely(t.task)) >> schedule(); > > > I think this if condition can also be removed. hrtimer_init_sleeper copies > the supplied task_struct * to the timer, which in this case is 'current'. > The check is likely to be there in case of !active case you removed. Yeah, it looks like we can get rid of this. Also, } while (t.task && pkt_dev->running && !signal_pending(current)); is present in the closing "}" of do-while loop and probably we don't need to check t.task here as well. And this review comment applies to patch 2/7 as well: hrtimer: don't check for active hrtimer after adding it I would still wait for somebody to prove us wrong :), and will resend it next week only. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On 09/07/14 11:44, Viresh Kumar wrote: > Hi Chris, > > On 9 July 2014 16:02, Chris Redpath <Chris.Redpath@arm.com> wrote: > >>> diff --git a/net/core/pktgen.c b/net/core/pktgen.c >>> index fc17a9d..f911acd 100644 >>> --- a/net/core/pktgen.c >>> +++ b/net/core/pktgen.c >>> @@ -2186,8 +2186,6 @@ static void spin(struct pktgen_dev *pkt_dev, ktime_t >>> spin_until) >>> do { >>> set_current_state(TASK_INTERRUPTIBLE); >>> hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS); >>> - if (!hrtimer_active(&t.timer)) >>> - t.task = NULL; >>> >>> if (likely(t.task)) >>> schedule(); >> >> >> I think this if condition can also be removed. hrtimer_init_sleeper copies >> the supplied task_struct * to the timer, which in this case is 'current'. >> The check is likely to be there in case of !active case you removed. > > Yeah, it looks like we can get rid of this. Also, > > } while (t.task && pkt_dev->running && !signal_pending(current)); > > is present in the closing "}" of do-while loop and probably we > don't need to check t.task here as well. > > And this review comment applies to patch 2/7 as well: > hrtimer: don't check for active hrtimer after adding it > > I would still wait for somebody to prove us wrong :), and will resend > it next week only. > > Thanks. > Yeah, no worries. I just happened to read it and not knowing any of the APIs had to look up what is going on. BTW, I *will* get back to you about that broadcast stuff when I get back to it myself. Other priorities at the moment again. --Chris -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
diff --git a/net/core/pktgen.c b/net/core/pktgen.c index fc17a9d..f911acd 100644 --- a/net/core/pktgen.c +++ b/net/core/pktgen.c @@ -2186,8 +2186,6 @@ static void spin(struct pktgen_dev *pkt_dev, ktime_t spin_until) do { set_current_state(TASK_INTERRUPTIBLE); hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS); - if (!hrtimer_active(&t.timer)) - t.task = NULL; if (likely(t.task)) schedule();
hrtimer_start*() family never fails to enqueue a hrtimer to a clock-base. The only special case is when the hrtimer was in past. If it is getting enqueued to local CPUs's clock-base, we raise a softirq and exit, else we handle that on next interrupt on remote CPU. At several places in the kernel, we try to make sure if hrtimer was added properly or not by calling hrtimer_active(), like: hrtimer_start(timer, expires, mode); if (hrtimer_active(timer)) { /* Added successfully */ } else { /* Was added in the past */ } As hrtimer_start*() never fails, hrtimer_active() is guaranteed to return '1'. So, there is no point calling hrtimer_active(). This patch updates net core to get this fixed. Cc: "David S. Miller" <davem@davemloft.net> Cc: netdev@vger.kernel.org Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> --- net/core/pktgen.c | 2 -- 1 file changed, 2 deletions(-)