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SubjectRe: [PATCH] output the cpu number when printking.
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Thanks randy's comments, I will modifiy it.

On Sun, 2012-12-23 at 19:37 -0800, Randy Dunlap wrote:
> On 12/23/12 18:31, he, bo wrote:
> > From: "he, bo" <bo.he@intel.com>
> >
> > We often hit kernel panic issues on SMP machines because processes race
> > on multiple cpu. By adding a new parameter printk.cpu, kernel prints
> > cpu number at printk information line. It’s useful to debug what cpus
> > are racing.
> >
> > Signed-off-by: he, bo <bo.he@intel.com>
> > ---
> > Documentation/kernel-parameters.txt | 4 ++++
> > kernel/printk.c | 18 ++++++++++++++++--
> > 2 files changed, 20 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> > index ddd84d6..ccd5266 100644
> > --- a/Documentation/kernel-parameters.txt
> > +++ b/Documentation/kernel-parameters.txt
> > @@ -2378,6 +2378,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> > printk.time= Show timing data prefixed to each printk message line
> > Format: <bool> (1/Y/y=enable, 0/N/n=disable)
> >
> > + printk.cpu= Show cpu data prefixed to each printk message line
> > + Format: <bool> (1/Y/y=enable, 0/N/n=disable)
> > + printk.cpu takes effect only when printk.time=y.
>
> Above line needs to be indented more (beginning under "Format:").
>
> > +
> > processor.max_cstate= [HW,ACPI]
> > Limit processor to maximum C-state
> > max_cstate=9 overrides any DMI blacklist limit.
> > diff --git a/kernel/printk.c b/kernel/printk.c
> > index 19c0d7b..873a226 100644
> > --- a/kernel/printk.c
> > +++ b/kernel/printk.c
> > @@ -863,9 +863,14 @@ static bool printk_time;
> > #endif
> > module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
> >
> > +static bool printk_cpu = 1;
> > +module_param_named(cpu, printk_cpu, bool, S_IRUGO | S_IWUSR);
> > +
> > static size_t print_time(u64 ts, char *buf)
> > {
> > unsigned long rem_nsec;
> > + size_t len = 0;
> > + int this_cpu;
> >
> > if (!printk_time)
> > return 0;
> > @@ -874,8 +879,17 @@ static size_t print_time(u64 ts, char *buf)
> > return 15;
> >
> > rem_nsec = do_div(ts, 1000000000);
> > - return sprintf(buf, "[%5lu.%06lu] ",
> > - (unsigned long)ts, rem_nsec / 1000);
> > +
> > + if (printk_cpu) {
> > + this_cpu = raw_smp_processor_id();
> > + len = sprintf(buf, "[%5lu.%06lu,%u] ",
> > + (unsigned long)ts, rem_nsec / 1000, this_cpu);
> > + } else {
> > + len = sprintf(buf, "[%5lu.%06lu] ",
> > + (unsigned long)ts, rem_nsec / 1000);
> > + }
> > +
> > + return len;
> > }
> >
> > static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
> >
>
>


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