On Thu, Aug 2, 2012 at 9:46 PM, Vikram Pandita <[email protected]> wrote: > From: Vikram Pandita <[email protected]> > > Introduce config option to enable CPU id reporting for printk() calls. > > Its sometimes very useful to have printk also print the CPU Identifier > that executed the call. This has helped to debug various SMP issues on > shipping > products. > > Known limitation is, if the system gets preempted between function call and > actual printk, the reported cpu-id might not be accurate. But most of the > times its seen to give a good feel of how the N cpu's in the system are > getting loaded. > > Signed-off-by: Vikram Pandita <[email protected]> > Cc: Mike Turquette <[email protected]> > Cc: Vimarsh Zutshi <[email protected]> > --- > kernel/printk.c | 20 ++++++++++++++++++++ > lib/Kconfig.debug | 13 +++++++++++++ > 2 files changed, 33 insertions(+) > > diff --git a/kernel/printk.c b/kernel/printk.c > index 6a76ab9..50feb82 100644 > --- a/kernel/printk.c > +++ b/kernel/printk.c > @@ -855,6 +855,25 @@ static size_t print_time(u64 ts, char *buf) > (unsigned long)ts, rem_nsec / 1000); > } > > +#if defined(CONFIG_PRINTK_CPUID) > +static bool printk_cpuid = 1; > +#else > +static bool printk_cpuid; > +#endif > +module_param_named(cpuid, printk_cpuid, bool, S_IRUGO | S_IWUSR); > + > +static size_t print_cpuid(char *buf) > +{ > + > + if (!printk_cpuid) > + return 0; > + > + if (!buf) > + return 4; > + > + return sprintf(buf, "[%1d] ", smp_processor_id()); > +} > + > static size_t print_prefix(const struct log *msg, bool syslog, char *buf) > { > size_t len = 0; > @@ -874,6 +893,7 @@ static size_t print_prefix(const struct log *msg, bool > syslog, char *buf) > } > } > > + len += print_cpuid(buf ? buf + len : NULL); > len += print_time(msg->ts_nsec, buf ? buf + len : NULL); > return len; > }
How is that supposed to be useful? The prefix is added while exporting data from the kmsg buffer, which is just the CPU that *reads* the data from the buffer, not the one that has *written* the data it into it. Do I miss anything here? Thanks, Kay -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
