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rcu: Add tracing to irq/NMI dyntick-idle transitions 

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2017-10-04 12:29:01 -07:00
parent 844ccdd7dc
commit bd2b879a1c
2 changed files with 14 additions and 6 deletions
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14
include/trace/events/rcu.h
View File

@ -421,16 +421,18 @@ TRACE_EVENT(rcu_fqs,
/*
* Tracepoint for dyntick-idle entry/exit events. These take a string
* as argument: "Start" for entering dyntick-idle mode, "End" for
* leaving it, "--=" for events moving towards idle, and "++=" for events
* moving away from idle. "Error on entry: not idle task" and "Error on
* exit: not idle task" indicate that a non-idle task is erroneously
* as argument: "Start" for entering dyntick-idle mode, "Startirq" for
* entering it from irq/NMI, "End" for leaving it, "Endirq" for leaving it
* to irq/NMI, "--=" for events moving towards idle, and "++=" for events
* moving away from idle. "Error on entry: not idle task" and "Error
* on exit: not idle task" indicate that a non-idle task is erroneously
* toying with the idle loop.
*
* These events also take a pair of numbers, which indicate the nesting
* depth before and after the event of interest. Note that task-related
* events use the upper bits of each number, while interrupt-related
* events use the lower bits.
* and interrupt-related events use two separate counters, and that the
* "++=" and "--=" events for irq/NMI will change the counter by two,
* otherwise by one.
*/
TRACE_EVENT(rcu_dyntick,

6
kernel/rcu/tree.c
View File

@ -880,12 +880,15 @@ void rcu_nmi_exit(void)
* leave it in non-RCU-idle state.
*/
if (rdtp->dynticks_nmi_nesting != 1) {
trace_rcu_dyntick(TPS("--="), rdtp->dynticks_nmi_nesting,
rdtp->dynticks_nmi_nesting - 2);
WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* No store tearing. */
rdtp->dynticks_nmi_nesting - 2);
return;
}
/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
trace_rcu_dyntick(TPS("Startirq"), rdtp->dynticks_nmi_nesting, 0);
WRITE_ONCE(rdtp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
rcu_dynticks_eqs_enter();
}
@ -1057,6 +1060,9 @@ void rcu_nmi_enter(void)
rcu_dynticks_eqs_exit();
incby = 1;
}
trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
rdtp->dynticks_nmi_nesting,
rdtp->dynticks_nmi_nesting + incby);
WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* Prevent store tearing. */
rdtp->dynticks_nmi_nesting + incby);
barrier();