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linux/include/trace/events/rcu.h
Paul E. McKenney 21e52e1566 rcu: Make RCU_FAST_NO_HZ handle timer migration 
The current RCU_FAST_NO_HZ assumes that timers do not migrate unless a
CPU goes offline, in which case it assumes that the CPU will have to come
out of dyntick-idle mode (cancelling the timer) in order to go offline.
This is important because when RCU_FAST_NO_HZ permits a CPU to enter
dyntick-idle mode despite having RCU callbacks pending, it posts a timer
on that CPU to force a wakeup on that CPU.  This wakeup ensures that the
CPU will eventually handle the end of the grace period, including invoking
its RCU callbacks.

However, Pascal Chapperon's test setup shows that the timer handler
rcu_idle_gp_timer_func() really does get invoked in some cases.  This is
problematic because this can cause the CPU that entered dyntick-idle
mode despite still having RCU callbacks pending to remain in
dyntick-idle mode indefinitely, which means that its RCU callbacks might
never be invoked.  This situation can result in grace-period delays or
even system hangs, which matches Pascal's observations of slow boot-up
and shutdown (https://lkml.org/lkml/2012/4/5/142).  See also the bugzilla:

	https://bugzilla.redhat.com/show_bug.cgi?id=806548

This commit therefore causes the "should never be invoked" timer handler
rcu_idle_gp_timer_func() to use smp_call_function_single() to wake up
the CPU for which the timer was intended, allowing that CPU to invoke
its RCU callbacks in a timely manner.

Reported-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-05-09 14:26:56 -07:00

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#undef TRACE_SYSTEM
#define TRACE_SYSTEM rcu
#if !defined(_TRACE_RCU_H) || defined(TRACE_HEADER_MULTI_READ)
#define _TRACE_RCU_H
#include <linux/tracepoint.h>
/*
* Tracepoint for start/end markers used for utilization calculations.
* By convention, the string is of the following forms:
*
* "Start <activity>" -- Mark the start of the specified activity,
* such as "context switch". Nesting is permitted.
* "End <activity>" -- Mark the end of the specified activity.
*
* An "@" character within "<activity>" is a comment character: Data
* reduction scripts will ignore the "@" and the remainder of the line.
*/
TRACE_EVENT(rcu_utilization,
TP_PROTO(char *s),
TP_ARGS(s),
TP_STRUCT__entry(
__field(char *, s)
),
TP_fast_assign(
__entry->s = s;
),
TP_printk("%s", __entry->s)
);
#ifdef CONFIG_RCU_TRACE
#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
/*
* Tracepoint for grace-period events: starting and ending a grace
* period ("start" and "end", respectively), a CPU noting the start
* of a new grace period or the end of an old grace period ("cpustart"
* and "cpuend", respectively), a CPU passing through a quiescent
* state ("cpuqs"), a CPU coming online or going offline ("cpuonl"
* and "cpuofl", respectively), and a CPU being kicked for being too
* long in dyntick-idle mode ("kick").
*/
TRACE_EVENT(rcu_grace_period,
TP_PROTO(char *rcuname, unsigned long gpnum, char *gpevent),
TP_ARGS(rcuname, gpnum, gpevent),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(unsigned long, gpnum)
__field(char *, gpevent)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->gpnum = gpnum;
__entry->gpevent = gpevent;
),
TP_printk("%s %lu %s",
__entry->rcuname, __entry->gpnum, __entry->gpevent)
);
/*
* Tracepoint for grace-period-initialization events. These are
* distinguished by the type of RCU, the new grace-period number, the
* rcu_node structure level, the starting and ending CPU covered by the
* rcu_node structure, and the mask of CPUs that will be waited for.
* All but the type of RCU are extracted from the rcu_node structure.
*/
TRACE_EVENT(rcu_grace_period_init,
TP_PROTO(char *rcuname, unsigned long gpnum, u8 level,
int grplo, int grphi, unsigned long qsmask),
TP_ARGS(rcuname, gpnum, level, grplo, grphi, qsmask),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(unsigned long, gpnum)
__field(u8, level)
__field(int, grplo)
__field(int, grphi)
__field(unsigned long, qsmask)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->gpnum = gpnum;
__entry->level = level;
__entry->grplo = grplo;
__entry->grphi = grphi;
__entry->qsmask = qsmask;
),
TP_printk("%s %lu %u %d %d %lx",
__entry->rcuname, __entry->gpnum, __entry->level,
__entry->grplo, __entry->grphi, __entry->qsmask)
);
/*
* Tracepoint for tasks blocking within preemptible-RCU read-side
* critical sections. Track the type of RCU (which one day might
* include SRCU), the grace-period number that the task is blocking
* (the current or the next), and the task's PID.
*/
TRACE_EVENT(rcu_preempt_task,
TP_PROTO(char *rcuname, int pid, unsigned long gpnum),
TP_ARGS(rcuname, pid, gpnum),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(unsigned long, gpnum)
__field(int, pid)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->gpnum = gpnum;
__entry->pid = pid;
),
TP_printk("%s %lu %d",
__entry->rcuname, __entry->gpnum, __entry->pid)
);
/*
* Tracepoint for tasks that blocked within a given preemptible-RCU
* read-side critical section exiting that critical section. Track the
* type of RCU (which one day might include SRCU) and the task's PID.
*/
TRACE_EVENT(rcu_unlock_preempted_task,
TP_PROTO(char *rcuname, unsigned long gpnum, int pid),
TP_ARGS(rcuname, gpnum, pid),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(unsigned long, gpnum)
__field(int, pid)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->gpnum = gpnum;
__entry->pid = pid;
),
TP_printk("%s %lu %d", __entry->rcuname, __entry->gpnum, __entry->pid)
);
/*
* Tracepoint for quiescent-state-reporting events. These are
* distinguished by the type of RCU, the grace-period number, the
* mask of quiescent lower-level entities, the rcu_node structure level,
* the starting and ending CPU covered by the rcu_node structure, and
* whether there are any blocked tasks blocking the current grace period.
* All but the type of RCU are extracted from the rcu_node structure.
*/
TRACE_EVENT(rcu_quiescent_state_report,
TP_PROTO(char *rcuname, unsigned long gpnum,
unsigned long mask, unsigned long qsmask,
u8 level, int grplo, int grphi, int gp_tasks),
TP_ARGS(rcuname, gpnum, mask, qsmask, level, grplo, grphi, gp_tasks),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(unsigned long, gpnum)
__field(unsigned long, mask)
__field(unsigned long, qsmask)
__field(u8, level)
__field(int, grplo)
__field(int, grphi)
__field(u8, gp_tasks)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->gpnum = gpnum;
__entry->mask = mask;
__entry->qsmask = qsmask;
__entry->level = level;
__entry->grplo = grplo;
__entry->grphi = grphi;
__entry->gp_tasks = gp_tasks;
),
TP_printk("%s %lu %lx>%lx %u %d %d %u",
__entry->rcuname, __entry->gpnum,
__entry->mask, __entry->qsmask, __entry->level,
__entry->grplo, __entry->grphi, __entry->gp_tasks)
);
/*
* Tracepoint for quiescent states detected by force_quiescent_state().
* These trace events include the type of RCU, the grace-period number
* that was blocked by the CPU, the CPU itself, and the type of quiescent
* state, which can be "dti" for dyntick-idle mode, "ofl" for CPU offline,
* or "kick" when kicking a CPU that has been in dyntick-idle mode for
* too long.
*/
TRACE_EVENT(rcu_fqs,
TP_PROTO(char *rcuname, unsigned long gpnum, int cpu, char *qsevent),
TP_ARGS(rcuname, gpnum, cpu, qsevent),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(unsigned long, gpnum)
__field(int, cpu)
__field(char *, qsevent)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->gpnum = gpnum;
__entry->cpu = cpu;
__entry->qsevent = qsevent;
),
TP_printk("%s %lu %d %s",
__entry->rcuname, __entry->gpnum,
__entry->cpu, __entry->qsevent)
);
#endif /* #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) */
/*
* 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
* 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.
*/
TRACE_EVENT(rcu_dyntick,
TP_PROTO(char *polarity, long long oldnesting, long long newnesting),
TP_ARGS(polarity, oldnesting, newnesting),
TP_STRUCT__entry(
__field(char *, polarity)
__field(long long, oldnesting)
__field(long long, newnesting)
),
TP_fast_assign(
__entry->polarity = polarity;
__entry->oldnesting = oldnesting;
__entry->newnesting = newnesting;
),
TP_printk("%s %llx %llx", __entry->polarity,
__entry->oldnesting, __entry->newnesting)
);
/*
* Tracepoint for RCU preparation for idle, the goal being to get RCU
* processing done so that the current CPU can shut off its scheduling
* clock and enter dyntick-idle mode. One way to accomplish this is
* to drain all RCU callbacks from this CPU, and the other is to have
* done everything RCU requires for the current grace period. In this
* latter case, the CPU will be awakened at the end of the current grace
* period in order to process the remainder of its callbacks.
*
* These tracepoints take a string as argument:
*
* "No callbacks": Nothing to do, no callbacks on this CPU.
* "In holdoff": Nothing to do, holding off after unsuccessful attempt.
* "Begin holdoff": Attempt failed, don't retry until next jiffy.
* "Dyntick with callbacks": Entering dyntick-idle despite callbacks.
* "More callbacks": Still more callbacks, try again to clear them out.
* "Callbacks drained": All callbacks processed, off to dyntick idle!
* "Timer": Timer fired to cause CPU to continue processing callbacks.
* "Demigrate": Timer fired on wrong CPU, woke up correct CPU.
* "Cleanup after idle": Idle exited, timer canceled.
*/
TRACE_EVENT(rcu_prep_idle,
TP_PROTO(char *reason),
TP_ARGS(reason),
TP_STRUCT__entry(
__field(char *, reason)
),
TP_fast_assign(
__entry->reason = reason;
),
TP_printk("%s", __entry->reason)
);
/*
* Tracepoint for the registration of a single RCU callback function.
* The first argument is the type of RCU, the second argument is
* a pointer to the RCU callback itself, the third element is the
* number of lazy callbacks queued, and the fourth element is the
* total number of callbacks queued.
*/
TRACE_EVENT(rcu_callback,
TP_PROTO(char *rcuname, struct rcu_head *rhp, long qlen_lazy,
long qlen),
TP_ARGS(rcuname, rhp, qlen_lazy, qlen),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(void *, rhp)
__field(void *, func)
__field(long, qlen_lazy)
__field(long, qlen)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->rhp = rhp;
__entry->func = rhp->func;
__entry->qlen_lazy = qlen_lazy;
__entry->qlen = qlen;
),
TP_printk("%s rhp=%p func=%pf %ld/%ld",
__entry->rcuname, __entry->rhp, __entry->func,
__entry->qlen_lazy, __entry->qlen)
);
/*
* Tracepoint for the registration of a single RCU callback of the special
* kfree() form. The first argument is the RCU type, the second argument
* is a pointer to the RCU callback, the third argument is the offset
* of the callback within the enclosing RCU-protected data structure,
* the fourth argument is the number of lazy callbacks queued, and the
* fifth argument is the total number of callbacks queued.
*/
TRACE_EVENT(rcu_kfree_callback,
TP_PROTO(char *rcuname, struct rcu_head *rhp, unsigned long offset,
long qlen_lazy, long qlen),
TP_ARGS(rcuname, rhp, offset, qlen_lazy, qlen),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(void *, rhp)
__field(unsigned long, offset)
__field(long, qlen_lazy)
__field(long, qlen)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->rhp = rhp;
__entry->offset = offset;
__entry->qlen_lazy = qlen_lazy;
__entry->qlen = qlen;
),
TP_printk("%s rhp=%p func=%ld %ld/%ld",
__entry->rcuname, __entry->rhp, __entry->offset,
__entry->qlen_lazy, __entry->qlen)
);
/*
* Tracepoint for marking the beginning rcu_do_batch, performed to start
* RCU callback invocation. The first argument is the RCU flavor,
* the second is the number of lazy callbacks queued, the third is
* the total number of callbacks queued, and the fourth argument is
* the current RCU-callback batch limit.
*/
TRACE_EVENT(rcu_batch_start,
TP_PROTO(char *rcuname, long qlen_lazy, long qlen, int blimit),
TP_ARGS(rcuname, qlen_lazy, qlen, blimit),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(long, qlen_lazy)
__field(long, qlen)
__field(int, blimit)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->qlen_lazy = qlen_lazy;
__entry->qlen = qlen;
__entry->blimit = blimit;
),
TP_printk("%s CBs=%ld/%ld bl=%d",
__entry->rcuname, __entry->qlen_lazy, __entry->qlen,
__entry->blimit)
);
/*
* Tracepoint for the invocation of a single RCU callback function.
* The first argument is the type of RCU, and the second argument is
* a pointer to the RCU callback itself.
*/
TRACE_EVENT(rcu_invoke_callback,
TP_PROTO(char *rcuname, struct rcu_head *rhp),
TP_ARGS(rcuname, rhp),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(void *, rhp)
__field(void *, func)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->rhp = rhp;
__entry->func = rhp->func;
),
TP_printk("%s rhp=%p func=%pf",
__entry->rcuname, __entry->rhp, __entry->func)
);
/*
* Tracepoint for the invocation of a single RCU callback of the special
* kfree() form. The first argument is the RCU flavor, the second
* argument is a pointer to the RCU callback, and the third argument
* is the offset of the callback within the enclosing RCU-protected
* data structure.
*/
TRACE_EVENT(rcu_invoke_kfree_callback,
TP_PROTO(char *rcuname, struct rcu_head *rhp, unsigned long offset),
TP_ARGS(rcuname, rhp, offset),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(void *, rhp)
__field(unsigned long, offset)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->rhp = rhp;
__entry->offset = offset;
),
TP_printk("%s rhp=%p func=%ld",
__entry->rcuname, __entry->rhp, __entry->offset)
);
/*
* Tracepoint for exiting rcu_do_batch after RCU callbacks have been
* invoked. The first argument is the name of the RCU flavor,
* the second argument is number of callbacks actually invoked,
* the third argument (cb) is whether or not any of the callbacks that
* were ready to invoke at the beginning of this batch are still
* queued, the fourth argument (nr) is the return value of need_resched(),
* the fifth argument (iit) is 1 if the current task is the idle task,
* and the sixth argument (risk) is the return value from
* rcu_is_callbacks_kthread().
*/
TRACE_EVENT(rcu_batch_end,
TP_PROTO(char *rcuname, int callbacks_invoked,
bool cb, bool nr, bool iit, bool risk),
TP_ARGS(rcuname, callbacks_invoked, cb, nr, iit, risk),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(int, callbacks_invoked)
__field(bool, cb)
__field(bool, nr)
__field(bool, iit)
__field(bool, risk)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->callbacks_invoked = callbacks_invoked;
__entry->cb = cb;
__entry->nr = nr;
__entry->iit = iit;
__entry->risk = risk;
),
TP_printk("%s CBs-invoked=%d idle=%c%c%c%c",
__entry->rcuname, __entry->callbacks_invoked,
__entry->cb ? 'C' : '.',
__entry->nr ? 'S' : '.',
__entry->iit ? 'I' : '.',
__entry->risk ? 'R' : '.')
);
/*
* Tracepoint for rcutorture readers. The first argument is the name
* of the RCU flavor from rcutorture's viewpoint and the second argument
* is the callback address.
*/
TRACE_EVENT(rcu_torture_read,
TP_PROTO(char *rcutorturename, struct rcu_head *rhp),
TP_ARGS(rcutorturename, rhp),
TP_STRUCT__entry(
__field(char *, rcutorturename)
__field(struct rcu_head *, rhp)
),
TP_fast_assign(
__entry->rcutorturename = rcutorturename;
__entry->rhp = rhp;
),
TP_printk("%s torture read %p",
__entry->rcutorturename, __entry->rhp)
);
#else /* #ifdef CONFIG_RCU_TRACE */
#define trace_rcu_grace_period(rcuname, gpnum, gpevent) do { } while (0)
#define trace_rcu_grace_period_init(rcuname, gpnum, level, grplo, grphi, \
qsmask) do { } while (0)
#define trace_rcu_preempt_task(rcuname, pid, gpnum) do { } while (0)
#define trace_rcu_unlock_preempted_task(rcuname, gpnum, pid) do { } while (0)
#define trace_rcu_quiescent_state_report(rcuname, gpnum, mask, qsmask, level, \
grplo, grphi, gp_tasks) do { } \
while (0)
#define trace_rcu_fqs(rcuname, gpnum, cpu, qsevent) do { } while (0)
#define trace_rcu_dyntick(polarity, oldnesting, newnesting) do { } while (0)
#define trace_rcu_prep_idle(reason) do { } while (0)
#define trace_rcu_callback(rcuname, rhp, qlen_lazy, qlen) do { } while (0)
#define trace_rcu_kfree_callback(rcuname, rhp, offset, qlen_lazy, qlen) \
do { } while (0)
#define trace_rcu_batch_start(rcuname, qlen_lazy, qlen, blimit) \
do { } while (0)
#define trace_rcu_invoke_callback(rcuname, rhp) do { } while (0)
#define trace_rcu_invoke_kfree_callback(rcuname, rhp, offset) do { } while (0)
#define trace_rcu_batch_end(rcuname, callbacks_invoked, cb, nr, iit, risk) \
do { } while (0)
#define trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
#endif /* #else #ifdef CONFIG_RCU_TRACE */
#endif /* _TRACE_RCU_H */
/* This part must be outside protection */
#include <trace/define_trace.h>
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