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SubjectRe: [PATCH] output the cpu number when printking.
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)
>


--
~Randy
--
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