Hi Mathieu,
Mathieu Desnoyers wrote:
>> static inline u32 trace_clock_read32(void)
>> {
>> - return get_cycles();
>> + if (likely(clock))
>> + return (u32) clock->read(clock);
>
> Can you walk us through the code that is executed when clock->read() is
> called ? Is it possible that the clock source read() takes a xtime seq
> read lock in some SH configurations ?
On SH, the trace_clock_read_synthetic_tsc invokes the
sh_tmu_clocksource_read (clock->read), in drivers/clocksource/sh_tmu.c.
This reads the timer counter register (TCNT).
What do you think?
Regards
Giuseppe
> If it is the case, then we will run into deadlocks with tracing code
> called from within the xtime seq write lock. Therefore, fixing this
> without calling the clocksource read() would be adequate.
>
> Thanks,
>
> Mathieu
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