[lttng-dev] sched_switch event

[Daniel.Thibault@drdc-rddc.gc.ca (Thibault, Daniel)]

-----Message d'origine-----
>   In linux-source-3.2.0/include/trace/events/sched.h, or
>   linux-headers-3.2.0-53/include/trace/events/sched.h, or
>   lttng-modules/instrumentation/events/mainline/sched.h,
>   we have in part:
>
>	TP_fast_assign(
>		memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
>		__entry->prev_pid	= prev->pid;
>		__entry->prev_prio	= prev->prio;
>		__entry->prev_state	= __trace_sched_switch_state(prev);
>		memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
>		__entry->next_pid	= next->pid;
>		__entry->next_prio	= next->prio;
>	),

   Scratch that, lttng-modules/instrumentation/events/lttng-module/sched.h has the same code, and I now realise the TP_fast_assign is not switching the prev_comm and next_comm fields (it is correctly mapping __entry->next_comm to next->comm), it's just that the copies are declared out of order.  TP_fast_assign is essentially a parallelised process.

   Sorry about the false alarm.

Daniel U. Thibault
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