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:
TRACE_EVENT(sched_switch,
TP_PROTO(struct task_struct *prev,
struct task_struct *next),
TP_ARGS(prev, next),
TP_STRUCT__entry(
__array( char, prev_comm, TASK_COMM_LEN )
__field( pid_t, prev_pid )
__field( int, prev_prio )
__field( long, prev_state )
__array( char, next_comm, TASK_COMM_LEN )
__field( pid_t, next_pid )
__field( int, next_prio )
),
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;
),
TP_printk("prev_comm=%s prev_pid=%d prev_prio=%d prev_state=%s%s ==>
next_comm=%s next_pid=%d next_prio=%d",
__entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
__entry->prev_state & (TASK_STATE_MAX-1) ?
__print_flags(__entry->prev_state & (TASK_STATE_MAX-1), "|",
{ 1, "S"} , { 2, "D" }, { 4, "T" }, { 8, "t" },
{ 16, "Z" }, { 32, "X" }, { 64, "x" },
{ 128, "W" }) : "R",
__entry->prev_state & TASK_STATE_MAX ? "+" : "",
__entry->next_comm, __entry->next_pid, __entry->next_prio)
);
Note how the TP_fast_assign lines are switching __entry->next_comm and
__entry->prev_comm, unlike the TP_printk lines.
In lttng-modules/instrumentation/events/lttng-module/sched.h, we find:
TP_STRUCT__entry(
__array_text( char, prev_comm, TASK_COMM_LEN )
__field( pid_t, prev_tid )
__field( int, prev_prio )
__field( long, prev_state )
__array_text( char, next_comm, TASK_COMM_LEN )
__field( pid_t, next_tid )
__field( int, next_prio )
),
Which is probably why nobody noticed this before, since LTTng traces
correctly identify the previous and next processes in the sched_switch event.
This is an upstream Linux kernel bug or what?
Another question is: if the kernel tracepoint event definitions appearing in
the source are ignored, why are they included at all?
Daniel U. Thibault
Protection des systèmes et contremesures (PSC) | Systems Protection &
Countermeasures (SPC)
Cyber sécurité pour les missions essentielles (CME) | Mission Critical Cyber
Security (MCCS)
R & D pour la défense Canada - Valcartier (RDDC Valcartier) | Defence R&D
Canada - Valcartier (DRDC Valcartier)
2459 route de la Bravoure
Québec QC G3J 1X5
CANADA
Vox : (418) 844-4000 x4245
Fax : (418) 844-4538
NAC : 918V QSDJ <http://www.travelgis.com/map.asp?addr=918V%20QSDJ>
Gouvernement du Canada | Government of Canada
<http://www.valcartier.drdc-rddc.gc.ca/>
_______________________________________________
lttng-dev mailing list
[email protected]
http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
