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Subject[RFC][PATCH 07/19] perf: Default PMU ops
Provide default implementations for the pmu txn methods, this allows
us to remove some conditional code.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
include/linux/perf_event.h | 10 +++----
kernel/perf_event.c | 64 ++++++++++++++++++++++++++++++++++++---------
2 files changed, 57 insertions(+), 17 deletions(-)

Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -656,21 +656,14 @@ group_sched_in(struct perf_event *group_
{
struct perf_event *event, *partial_group = NULL;
struct pmu *pmu = group_event->pmu;
- bool txn = false;

if (group_event->state == PERF_EVENT_STATE_OFF)
return 0;

- /* Check if group transaction availabe */
- if (pmu->start_txn)
- txn = true;
-
- if (txn)
- pmu->start_txn(pmu);
+ pmu->start_txn(pmu);

if (event_sched_in(group_event, cpuctx, ctx)) {
- if (txn)
- pmu->cancel_txn(pmu);
+ pmu->cancel_txn(pmu);
return -EAGAIN;
}

@@ -684,7 +677,7 @@ group_sched_in(struct perf_event *group_
}
}

- if (!txn || !pmu->commit_txn(pmu))
+ if (!pmu->commit_txn(pmu))
return 0;

group_error:
@@ -699,8 +692,7 @@ group_error:
}
event_sched_out(group_event, cpuctx, ctx);

- if (txn)
- pmu->cancel_txn(pmu);
+ pmu->cancel_txn(pmu);

return -EAGAIN;
}
@@ -4755,6 +4747,31 @@ static LIST_HEAD(pmus);
static DEFINE_MUTEX(pmus_lock);
static struct srcu_struct pmus_srcu;

+static void perf_pmu_nop_void(struct pmu *pmu)
+{
+}
+
+static int perf_pmu_nop_int(struct pmu *pmu)
+{
+ return 0;
+}
+
+static void perf_pmu_start_txn(struct pmu *pmu)
+{
+ perf_pmu_disable(pmu);
+}
+
+static int perf_pmu_commit_txn(struct pmu *pmu)
+{
+ perf_pmu_enable(pmu);
+ return 0;
+}
+
+static void perf_pmu_cancel_txn(struct pmu *pmu)
+{
+ perf_pmu_enable(pmu);
+}
+
int perf_pmu_register(struct pmu *pmu)
{
int ret;
@@ -4764,6 +4781,29 @@ int perf_pmu_register(struct pmu *pmu)
pmu->pmu_disable_count = alloc_percpu(int);
if (!pmu->pmu_disable_count)
goto unlock;
+
+ if (!pmu->start_txn) {
+ if (pmu->pmu_enable) {
+ /*
+ * If we have pmu_enable/pmu_disable calls, install
+ * transaction stubs that use that to try and batch
+ * hardware accesses.
+ */
+ pmu->start_txn = perf_pmu_start_txn;
+ pmu->commit_txn = perf_pmu_commit_txn;
+ pmu->cancel_txn = perf_pmu_cancel_txn;
+ } else {
+ pmu->start_txn = perf_pmu_nop_void;
+ pmu->commit_txn = perf_pmu_nop_int;
+ pmu->cancel_txn = perf_pmu_nop_void;
+ }
+ }
+
+ if (!pmu->pmu_enable) {
+ pmu->pmu_enable = perf_pmu_nop_void;
+ pmu->pmu_disable = perf_pmu_nop_void;
+ }
+
list_add_rcu(&pmu->entry, &pmus);
ret = 0;
unlock:
Index: linux-2.6/include/linux/perf_event.h
===================================================================
--- linux-2.6.orig/include/linux/perf_event.h
+++ linux-2.6/include/linux/perf_event.h
@@ -565,8 +565,8 @@ struct pmu {

int *pmu_disable_count;

- void (*pmu_enable) (struct pmu *pmu);
- void (*pmu_disable) (struct pmu *pmu);
+ void (*pmu_enable) (struct pmu *pmu); /* optional */
+ void (*pmu_disable) (struct pmu *pmu); /* optional */

/*
* Should return -ENOENT when the @event doesn't match this PMU.
@@ -590,19 +590,19 @@ struct pmu {
* Start the transaction, after this ->enable() doesn't need to
* do schedulability tests.
*/
- void (*start_txn) (struct pmu *pmu);
+ void (*start_txn) (struct pmu *pmu); /* optional */
/*
* If ->start_txn() disabled the ->enable() schedulability test
* then ->commit_txn() is required to perform one. On success
* the transaction is closed. On error the transaction is kept
* open until ->cancel_txn() is called.
*/
- int (*commit_txn) (struct pmu *pmu);
+ int (*commit_txn) (struct pmu *pmu); /* optional */
/*
* Will cancel the transaction, assumes ->disable() is called
* for each successfull ->enable() during the transaction.
*/
- void (*cancel_txn) (struct pmu *pmu);
+ void (*cancel_txn) (struct pmu *pmu); /* optional */
};

/**



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