perf/core: Drop PERF_EVENT_TXN

We currently use PERF_EVENT_TXN flag to determine if we are in the middle
of a transaction. If in a transaction, we defer the schedulability checks
from pmu->add() operation to the pmu->commit() operation.

Now that we have "transaction types" (PERF_PMU_TXN_ADD, PERF_PMU_TXN_READ)
we can use the type to determine if we are in a transaction and drop the
PERF_EVENT_TXN flag.

When PERF_EVENT_TXN is dropped, the cpuhw->group_flag on some architectures
becomes unused, so drop that field as well.

This is an extension of the Powerpc patch from Peter Zijlstra to s390,
Sparc and x86 architectures.

Signed-off-by: Sukadev Bhattiprolu <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Vince Weaver <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/powerpc/perf/core-book3s.c

···
 	unsigned long amasks[MAX_HWEVENTS][MAX_EVENT_ALTERNATIVES];
 	unsigned long avalues[MAX_HWEVENTS][MAX_EVENT_ALTERNATIVES];
 
-	unsigned int group_flag;
 	unsigned int txn_flags;
 	int n_txn_start;
 
···
 	 * skip the schedulability test here, it will be performed
 	 * at commit time(->commit_txn) as a whole
 	 */
-	if (cpuhw->group_flag & PERF_EVENT_TXN)
+	if (cpuhw->txn_flags & PERF_PMU_TXN_ADD)
 		goto nocheck;
 
 	if (check_excludes(cpuhw->event, cpuhw->flags, n0, 1))
···
 		return;
 
 	perf_pmu_disable(pmu);
-	cpuhw->group_flag |= PERF_EVENT_TXN;
 	cpuhw->n_txn_start = cpuhw->n_events;
 }
 
···
 	if (txn_flags & ~PERF_PMU_TXN_ADD)
 		return;
 
-	cpuhw->group_flag &= ~PERF_EVENT_TXN;
 	perf_pmu_enable(pmu);
 }
 
···
 	for (i = cpuhw->n_txn_start; i < n; ++i)
 		cpuhw->event[i]->hw.config = cpuhw->events[i];
 
-	cpuhw->group_flag &= ~PERF_EVENT_TXN;
 	cpuhw->txn_flags = 0;
 	perf_pmu_enable(pmu);
 	return 0;

arch/s390/kernel/perf_cpum_cf.c

···
 	 * For group events transaction, the authorization check is
 	 * done in cpumf_pmu_commit_txn().
 	 */
-	if (!(cpuhw->flags & PERF_EVENT_TXN))
+	if (!(cpuhw->txn_flags & PERF_PMU_TXN_ADD))
 		if (validate_ctr_auth(&event->hw))
 			return -EPERM;
 
···
 		return;
 
 	perf_pmu_disable(pmu);
-	cpuhw->flags |= PERF_EVENT_TXN;
 	cpuhw->tx_state = cpuhw->state;
 }
 
···
 
 	WARN_ON(cpuhw->tx_state != cpuhw->state);
 
-	cpuhw->flags &= ~PERF_EVENT_TXN;
 	perf_pmu_enable(pmu);
 }
 
···
 	if ((state & cpuhw->info.auth_ctl) != state)
 		return -EPERM;
 
-	cpuhw->flags &= ~PERF_EVENT_TXN;
 	cpuhw->txn_flags = 0;
 	perf_pmu_enable(pmu);
 	return 0;

arch/sparc/kernel/perf_event.c

···
 	/* Enabled/disable state.  */
 	int			enabled;
 
-	unsigned int		group_flag;
 	unsigned int		txn_flags;
 };
 static DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events) = { .enabled = 1, };
···
 	 * skip the schedulability test here, it will be performed
 	 * at commit time(->commit_txn) as a whole
 	 */
-	if (cpuc->group_flag & PERF_EVENT_TXN)
+	if (cpuc->txn_flags & PERF_PMU_TXN_ADD)
 		goto nocheck;
 
 	if (check_excludes(cpuc->event, n0, 1))
···
 		return;
 
 	perf_pmu_disable(pmu);
-	cpuhw->group_flag |= PERF_EVENT_TXN;
 }
 
 /*
···
 	if (txn_flags & ~PERF_PMU_TXN_ADD)
 		return;
 
-	cpuhw->group_flag &= ~PERF_EVENT_TXN;
 	perf_pmu_enable(pmu);
 }
 
···
 	if (sparc_check_constraints(cpuc->event, cpuc->events, n))
 		return -EAGAIN;
 
-	cpuc->group_flag &= ~PERF_EVENT_TXN;
 	cpuc->txn_flags = 0;
 	perf_pmu_enable(pmu);
 	return 0;

arch/x86/kernel/cpu/perf_event.c

···
 	 * skip the schedulability test here, it will be performed
 	 * at commit time (->commit_txn) as a whole.
 	 */
-	if (cpuc->group_flag & PERF_EVENT_TXN)
+	if (cpuc->txn_flags & PERF_PMU_TXN_ADD)
 		goto done_collect;
 
 	ret = x86_pmu.schedule_events(cpuc, n, assign);
···
 	 * XXX assumes any ->del() called during a TXN will only be on
 	 * an event added during that same TXN.
 	 */
-	if (cpuc->group_flag & PERF_EVENT_TXN)
+	if (cpuc->txn_flags & PERF_PMU_TXN_ADD)
 		return;
 
 	/*
···
 		return;
 
 	perf_pmu_disable(pmu);
-	__this_cpu_or(cpu_hw_events.group_flag, PERF_EVENT_TXN);
 	__this_cpu_write(cpu_hw_events.n_txn, 0);
 }
 
···
 	if (txn_flags & ~PERF_PMU_TXN_ADD)
 		return;
 
-	__this_cpu_and(cpu_hw_events.group_flag, ~PERF_EVENT_TXN);
 	/*
 	 * Truncate collected array by the number of events added in this
 	 * transaction. See x86_pmu_add() and x86_pmu_*_txn().
···
 	 */
 	memcpy(cpuc->assign, assign, n*sizeof(int));
 
-	cpuc->group_flag &= ~PERF_EVENT_TXN;
 	cpuc->txn_flags = 0;
 	perf_pmu_enable(pmu);
 	return 0;

arch/x86/kernel/cpu/perf_event.h

···
 
 	int			n_excl; /* the number of exclusive events */
 
-	unsigned int		group_flag;
 	unsigned int		txn_flags;
 	int			is_fake;
 

include/linux/perf_event.h

···
 /*
  * Common implementation detail of pmu::{start,commit,cancel}_txn
  */
-#define PERF_EVENT_TXN 0x1
-
 #define PERF_PMU_TXN_ADD  0x1		/* txn to add/schedule event on PMU */
 #define PERF_PMU_TXN_READ 0x2		/* txn to read event group from PMU */