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...@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...@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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