Messages in this thread Patch in this message | | | Date | Mon, 04 Jun 2012 10:22:28 +0800 | From | Chen Gong <> | Subject | Re: [patch 1/2] x86: mce Cleanup timer mess |
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Hi, Tony and Thomas
This patch has been merged, but It still have some confusion, please see inline comment and give me some explanation.
于 2012/5/25 1:54, Thomas Gleixner 写道: > Use unsigned long for dealing with jiffies not int. Rename the > callback to something sensible. Use __this_cpu_read/write for > accessing per cpu data. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- > arch/x86/kernel/cpu/mcheck/mce.c | 31 > ++++++++++++++++--------------- 1 file changed, 16 insertions(+), > 15 deletions(-) > > Index: linux-2.6/arch/x86/kernel/cpu/mcheck/mce.c > =================================================================== > > > --- linux-2.6.orig/arch/x86/kernel/cpu/mcheck/mce.c > +++ linux-2.6/arch/x86/kernel/cpu/mcheck/mce.c @@ -1237,15 > +1237,15 @@ void mce_log_therm_throt_event(__u64 sta * poller finds > an MCE, poll 2x faster. When the poller finds no more * errors, > poll 2x slower (up to check_interval seconds). */ -static int > check_interval = 5 * 60; /* 5 minutes */ +static unsigned long > check_interval = 5 * 60; /* 5 minutes */ > > -static DEFINE_PER_CPU(int, mce_next_interval); /* in jiffies */ > +static DEFINE_PER_CPU(unsigned long, mce_next_interval); /* in > jiffies */ static DEFINE_PER_CPU(struct timer_list, mce_timer); > > -static void mce_start_timer(unsigned long data) +static void > mce_timer_fn(unsigned long data) { - struct timer_list *t = > &per_cpu(mce_timer, data); - int *n; + struct timer_list *t = > &__get_cpu_var(mce_timer); + unsigned long iv; > > WARN_ON(smp_processor_id() != data); > > @@ -1258,13 +1258,14 @@ static void mce_start_timer(unsigned lon * > Alert userspace if needed. If we logged an MCE, reduce the * > polling interval, otherwise increase the polling interval. */ - n > = &__get_cpu_var(mce_next_interval); + iv = > __this_cpu_read(mce_next_interval); if (mce_notify_irq()) - *n = > max(*n/2, HZ/100); + iv = max(iv, (unsigned long) HZ/100);
Here Thomas changed original mode from "*n = max(*n/2, HZ/100);" to "iv = max(iv, (unsigned long) HZ/100);", which means *iv* will not be decremented but only incremented in _else_ branch. If so, eventually the *iv will be equal to *check_interval*. I don't think it makes sense. Even we use new logic, the comment before these codes should be updated.
So Thomas, would you please explain why you use this new logic?
> else - *n = min(*n*2, > (int)round_jiffies_relative(check_interval*HZ)); + iv = min(iv * > 2, round_jiffies_relative(check_interval * HZ)); + > __this_cpu_write(mce_next_interval, iv); > > - t->expires = jiffies + *n; + t->expires = jiffies + iv; > add_timer_on(t, smp_processor_id()); } > > @@ -1542,17 +1543,17 @@ static void __mcheck_cpu_init_vendor(str > static void __mcheck_cpu_init_timer(void) { struct timer_list *t = > &__get_cpu_var(mce_timer); - int *n = > &__get_cpu_var(mce_next_interval); + unsigned long iv = > __this_cpu_read(mce_next_interval); > > - setup_timer(t, mce_start_timer, smp_processor_id()); + > setup_timer(t, mce_timer_fn, smp_processor_id()); > > if (mce_ignore_ce) return; > > - *n = check_interval * HZ; - if (!*n) + > __this_cpu_write(mce_next_interval, iv); + if (!iv) return; - > t->expires = round_jiffies(jiffies + *n); + t->expires = > round_jiffies(jiffies + iv); add_timer_on(t, smp_processor_id()); > } > > @@ -2262,7 +2263,7 @@ mce_cpu_callback(struct notifier_block * > case CPU_DOWN_FAILED_FROZEN: if (!mce_ignore_ce && check_interval) > { t->expires = round_jiffies(jiffies + - > __get_cpu_var(mce_next_interval)); + > per_cpu(mce_next_interval, cpu)); add_timer_on(t, cpu); } > smp_call_function_single(cpu, mce_reenable_cpu, &action, 1); > > >
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