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SubjectRe: [PATCH/RFC v9 2/2] Use trace events to report stalls
On Wed, Aug 17, 2011 at 01:36:09PM -0700, Alex Neronskiy wrote:
> Signed-off-by: Alex Neronskiy <zakmagnus@chromium.org>
> ---
> This outputs both the numerical representation of the stall as well
> as a stack trace. The trace, unlike the number, is always output,
> regardless of what debug/tracing/events/watchdog/enable says. I
> don't know how to hook into that.
>

(adding Steve to 'cc)

Yes, it would be nice to make the dump stack contigent on the
tracepoints...that's what you want?

If so, maybe we could have TP_fast_assign fill a buffer which is output
via TP_printk, or else TP_printk could take an optional callback
function...

Thanks,

-Jason


> kernel/trace_watchdog.h | 43 +++++++++++++++++++++++++++++++++++++++++++
> kernel/watchdog.c | 23 +++++++++++------------
> 2 files changed, 54 insertions(+), 12 deletions(-)
> create mode 100644 kernel/trace_watchdog.h
>
> diff --git a/kernel/trace_watchdog.h b/kernel/trace_watchdog.h
> new file mode 100644
> index 0000000..1401d27f
> --- /dev/null
> +++ b/kernel/trace_watchdog.h
> @@ -0,0 +1,43 @@
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM watchdog
> +
> +#if !defined(_TRACE_WATCHDOG_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_WATCHDOG_H
> +
> +#include <linux/tracepoint.h>
> +#include <linux/stacktrace.h>
> +
> +TRACE_EVENT(soft_stall,
> + TP_PROTO(unsigned long stall),
> + TP_ARGS(stall),
> + TP_STRUCT__entry(
> + __field(unsigned long, stall)
> + ),
> + TP_fast_assign(
> + __entry->stall = stall;
> + ),
> + TP_printk("Soft stall: %lums", __entry->stall)
> +);
> +
> +#ifdef CONFIG_HARDLOCKUP_DETECTOR
> +TRACE_EVENT(hard_stall,
> + TP_PROTO(unsigned long stall),
> + TP_ARGS(stall),
> + TP_STRUCT__entry(
> + __field(unsigned long, stall)
> + ),
> + TP_fast_assign(
> + __entry->stall = stall;
> + ),
> + TP_printk("Hard stall: %lu", __entry->stall)
> +);
> +#endif /* CONFIG_HARDLOCKUP_DETECTOR */
> +
> +#endif /* _TRACE_WATCHDOG_H */
> +
> +#undef TRACE_INCLUDE_PATH
> +#undef TRACE_INCLUDE_FILE
> +#define TRACE_INCLUDE_PATH .
> +
> +#define TRACE_INCLUDE_FILE trace_watchdog
> +#include <trace/define_trace.h>
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index d4c51cc..18385ed 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -27,6 +27,9 @@
> #include <asm/irq_regs.h>
> #include <linux/perf_event.h>
>
> +#define CREATE_TRACE_POINTS
> +#include "trace_watchdog.h"
> +
> int watchdog_enabled = 1;
> int __read_mostly watchdog_thresh = 10;
> static unsigned long worst_softstall;
> @@ -208,7 +211,7 @@ void touch_softlockup_watchdog_sync(void)
>
> #ifdef CONFIG_HARDLOCKUP_DETECTOR
> /* watchdog detector functions */
> -static void update_hardstall(unsigned long stall, int this_cpu)
> +static void update_hardstall(unsigned long stall)
> {
> int update_stall = 0;
>
> @@ -222,10 +225,8 @@ static void update_hardstall(unsigned long stall, int this_cpu)
> }
>
> if (update_stall) {
> - printk(KERN_WARNING "LOCKUP may be in progress!"
> - "Worst hard stall seen on CPU#%d: %lu interrupts missed\n",
> - this_cpu, stall);
> - dump_stack();
> + trace_hard_stall(stall);
> + trace_dump_stack();
> }
> }
>
> @@ -245,12 +246,12 @@ static int is_hardlockup(int this_cpu)
> if (ints_missed >= hardlockup_thresh)
> return 1;
>
> - update_hardstall(ints_missed, this_cpu);
> + update_hardstall(ints_missed);
> return 0;
> }
> #endif
>
> -static void update_softstall(unsigned long stall, int this_cpu)
> +static void update_softstall(unsigned long stall)
> {
> int update_stall = 0;
> if (stall > get_softstall_thresh() &&
> @@ -264,10 +265,8 @@ static void update_softstall(unsigned long stall, int this_cpu)
> }
>
> if (update_stall) {
> - printk(KERN_WARNING "LOCKUP may be in progress!"
> - "Worst soft stall seen on CPU#%d: %lums\n",
> - this_cpu, stall);
> - dump_stack();
> + trace_soft_stall(stall);
> + trace_dump_stack();
> }
> }
>
> @@ -280,7 +279,7 @@ static int is_softlockup(unsigned long touch_ts, int this_cpu)
> if (time_after(now, touch_ts + 1000 * get_softlockup_thresh()))
> return stall;
>
> - update_softstall(stall, this_cpu);
> + update_softstall(stall);
>
> return 0;
> }
> --
> 1.7.3.1
>
> --
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