From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: tglx@linutronix.de, linaro-kernel@lists.linaro.org,
linux-kernel@vger.kernel.org, fweisbec@gmail.com,
linaro-networking@linaro.org
Subject: Re: [PATCH 04/14] hrtimer: use base->index instead of basenum in switch_hrtimer_base()
Date: Wed, 26 Mar 2014 17:13:12 +0530 [thread overview]
Message-ID: <5332BD50.1070600@linux.vnet.ibm.com> (raw)
In-Reply-To: <535a552cd2c05a3ae2cb61da2583646e1c649699.1395832156.git.viresh.kumar@linaro.org>
On 03/26/2014 04:51 PM, Viresh Kumar wrote:
> In switch_hrtimer_base() we have created a local variable basenum which is set
> to base->index. This variable is used at only one place. It makes code more
> readable if we remove this variable use base->index directly.
>
No, this doesn't look right. Note that the code can re-execute
the assignment to new_base, by jumping to the 'again' label.
See below.
> --- a/kernel/hrtimer.c
> +++ b/kernel/hrtimer.c
> @@ -202,11 +202,10 @@ switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
> struct hrtimer_cpu_base *new_cpu_base;
> int this_cpu = smp_processor_id();
> int cpu = get_nohz_timer_target(pinned);
> - int basenum = base->index;
>
> again:
> new_cpu_base = &per_cpu(hrtimer_bases, cpu);
> - new_base = &new_cpu_base->clock_base[basenum];
> + new_base = &new_cpu_base->clock_base[base->index];
>
Further down, timer->base can be altered (and set to NULL too).
So if we jump back to 'again', we'll end up in trouble.
So I think its important to cache the value in basenum and
use it.
> if (base != new_base) {
> /*
>
Regards,
Srivatsa S. Bhat
next prev parent reply other threads:[~2014-03-26 11:43 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-26 11:21 [PATCH 00/14] timers/hrtimers: Minor cleanups Viresh Kumar
2014-03-26 11:21 ` [PATCH 01/14] hrtimer: replace 'tab' with 'space' after 'comma' Viresh Kumar
2014-03-26 11:21 ` [PATCH 02/14] hrtimer: Coalesce format fragments in printk() Viresh Kumar
2014-03-26 11:21 ` [PATCH 03/14] hrtimer: call hrtimer_set_expires_range() from hrtimer_set_expires_range_ns() Viresh Kumar
2014-03-26 11:21 ` [PATCH 04/14] hrtimer: use base->index instead of basenum in switch_hrtimer_base() Viresh Kumar
2014-03-26 11:43 ` Srivatsa S. Bhat [this message]
2014-03-26 14:08 ` [LNG] " Viresh Kumar
2014-03-26 17:31 ` Thomas Gleixner
2014-03-26 17:57 ` Srivatsa S. Bhat
2014-03-26 11:21 ` [PATCH 05/14] hrtimer: no need to rewrite '1' to hrtimer_hres_enabled Viresh Kumar
2014-03-26 11:21 ` [PATCH 06/14] hrtimer: don't rewrite same value to expires_next in hrtimer_force_reprogram() Viresh Kumar
2014-03-26 11:21 ` [PATCH 07/14] hrtimer: use base->hres_active directly instead of hrtimer_hres_active() Viresh Kumar
2014-03-26 11:21 ` [PATCH 08/14] hrtimer: remove dummy definition of hrtimer_force_reprogram() Viresh Kumar
2014-03-26 11:21 ` [PATCH 09/14] hrtimer: don't check state of base->hres_active in hrtimer_switch_to_hres() Viresh Kumar
2014-03-26 11:21 ` [PATCH 10/14] hrtimer: remove clock_was_set_delayed() from hrtimer.h Viresh Kumar
2014-03-26 11:21 ` [PATCH 11/14] hrtimer: remove active_bases field from struct hrtimer_cpu_base Viresh Kumar
2014-03-26 17:28 ` Thomas Gleixner
2014-03-27 4:30 ` Viresh Kumar
2014-03-26 11:21 ` [PATCH 12/14] hrtimer: don't emulate notifier call to initialize timer base Viresh Kumar
2014-03-26 12:40 ` Srivatsa S. Bhat
2014-03-26 14:17 ` [LNG] " Viresh Kumar
2014-03-26 11:21 ` [PATCH 13/14] timer: simplify CPU_UP_PREPARE notifier code path Viresh Kumar
2014-03-26 12:47 ` Srivatsa S. Bhat
2014-03-26 11:21 ` [PATCH 14/14] timer: don't emulate notifier call to initialize timer base Viresh Kumar
2014-03-26 12:43 ` Srivatsa S. Bhat
2014-03-27 5:23 ` [PATCH 1/2] hrtimer: don't add clock-base to active_bases if already present Viresh Kumar
2014-03-27 5:23 ` [PATCH V2 2/2] hrtimer: use __ffs() to iterate over valid bits from active_bases Viresh Kumar
2014-03-27 5:40 ` Thomas Gleixner
2014-03-27 5:46 ` Viresh Kumar
2014-03-27 5:49 ` [PATCH V3] " Viresh Kumar
2014-03-27 5:54 ` [PATCH V3 Resend] hrtimer: use ffs() " Viresh Kumar
2014-03-27 5:39 ` [PATCH 1/2] hrtimer: don't add clock-base to active_bases if already present Thomas Gleixner
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