[tip: perf/core] perf: Clean up pmu specific data

tip-bot2 for Kan Liang
2025-03-17T10:34:09Z

The following commit has been merged into the perf/core branch of tip:

Commit-ID: bd2da08d9363d191551d79e5b04121348e18af5a
Gitweb: https://git.kernel.org/tip/bd2da08d9363d191551d79e5b04121348e18af5a
Author: Kan Liang <kan.liang@linux.intel.com>
AuthorDate: Fri, 14 Mar 2025 10:27:00 -07:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 17 Mar 2025 11:23:38 +01:00

perf: Clean up pmu specific data

The pmu specific data is saved in task_struct now. Remove it from event
context structure.

Remove swap_task_ctx() as well.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250314172700.438923-7-kan.liang@linux.intel.com
---
include/linux/perf_event.h | 12 +------
kernel/events/core.c | 76 +------------------------------------
2 files changed, 3 insertions(+), 85 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 58f40c8..5b8e3aa 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -502,16 +502,6 @@ struct pmu {
struct kmem_cache *task_ctx_cache;

/*
- * PMU specific parts of task perf event context (i.e. ctx->task_ctx_data)
- * can be synchronized using this function. See Intel LBR callstack support
- * implementation and Perf core context switch handling callbacks for usage
- * examples.
- */
- void (*swap_task_ctx) (struct perf_event_pmu_context *prev_epc,
- struct perf_event_pmu_context *next_epc);
- /* optional */
-
- /*
* Set up pmu-private data structures for an AUX area
*/
void *(*setup_aux) (struct perf_event *event, void **pages,
@@ -933,7 +923,6 @@ struct perf_event_pmu_context {
atomic_t refcount; /* event <-> epc */
struct rcu_head rcu_head;

- void *task_ctx_data; /* pmu specific data */
/*
* Set when one or more (plausibly active) event can't be scheduled
* due to pmu overcommit or pmu constraints, except tolerant to
@@ -981,7 +970,6 @@ struct perf_event_context {
int nr_user;
int is_active;

- int nr_task_data;
int nr_stat;
int nr_freq;
int rotate_disable;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 9928292..4ce9795 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1254,20 +1254,6 @@ static void get_ctx(struct perf_event_context *ctx)
refcount_inc(&ctx->refcount);
}

-static void *alloc_task_ctx_data(struct pmu *pmu)
-{
- if (pmu->task_ctx_cache)
- return kmem_cache_zalloc(pmu->task_ctx_cache, GFP_KERNEL);
-
- return NULL;
-}
-
-static void free_task_ctx_data(struct pmu *pmu, void *task_ctx_data)
-{
- if (pmu->task_ctx_cache && task_ctx_data)
- kmem_cache_free(pmu->task_ctx_cache, task_ctx_data);
-}
-
static void free_ctx(struct rcu_head *head)
{
struct perf_event_context *ctx;
@@ -3577,42 +3563,6 @@ static void perf_event_sync_stat(struct perf_event_context *ctx,
}
}

-#define double_list_for_each_entry(pos1, pos2, head1, head2, member) \
- for (pos1 = list_first_entry(head1, typeof(*pos1), member), \
- pos2 = list_first_entry(head2, typeof(*pos2), member); \
- !list_entry_is_head(pos1, head1, member) && \
- !list_entry_is_head(pos2, head2, member); \
- pos1 = list_next_entry(pos1, member), \
- pos2 = list_next_entry(pos2, member))
-
-static void perf_event_swap_task_ctx_data(struct perf_event_context *prev_ctx,
- struct perf_event_context *next_ctx)
-{
- struct perf_event_pmu_context *prev_epc, *next_epc;
-
- if (!prev_ctx->nr_task_data)
- return;
-
- double_list_for_each_entry(prev_epc, next_epc,
- &prev_ctx->pmu_ctx_list, &next_ctx->pmu_ctx_list,
- pmu_ctx_entry) {
-
- if (WARN_ON_ONCE(prev_epc->pmu != next_epc->pmu))
- continue;
-
- /*
- * PMU specific parts of task perf context can require
- * additional synchronization. As an example of such
- * synchronization see implementation details of Intel
- * LBR call stack data profiling;
- */
- if (prev_epc->pmu->swap_task_ctx)
- prev_epc->pmu->swap_task_ctx(prev_epc, next_epc);
- else
- swap(prev_epc->task_ctx_data, next_epc->task_ctx_data);
- }
-}
-
static void perf_ctx_sched_task_cb(struct perf_event_context *ctx,
struct task_struct *task, bool sched_in)
{
@@ -3687,16 +3637,15 @@ perf_event_context_sched_out(struct task_struct *task, struct task_struct *next)
WRITE_ONCE(next_ctx->task, task);

perf_ctx_sched_task_cb(ctx, task, false);
- perf_event_swap_task_ctx_data(ctx, next_ctx);

perf_ctx_enable(ctx, false);

/*
* RCU_INIT_POINTER here is safe because we've not
* modified the ctx and the above modification of
- * ctx->task and ctx->task_ctx_data are immaterial
- * since those values are always verified under
- * ctx->lock which we're now holding.
+ * ctx->task is immaterial since this value is
+ * always verified under ctx->lock which we're now
+ * holding.
*/
RCU_INIT_POINTER(task->perf_event_ctxp, next_ctx);
RCU_INIT_POINTER(next->perf_event_ctxp, ctx);
@@ -5005,7 +4954,6 @@ find_get_pmu_context(struct pmu *pmu, struct perf_event_context *ctx,
struct perf_event *event)
{
struct perf_event_pmu_context *new = NULL, *pos = NULL, *epc;
- void *task_ctx_data = NULL;

if (!ctx->task) {
/*
@@ -5038,14 +4986,6 @@ find_get_pmu_context(struct pmu *pmu, struct perf_event_context *ctx,
if (!new)
return ERR_PTR(-ENOMEM);

- if (event->attach_state & PERF_ATTACH_TASK_DATA) {
- task_ctx_data = alloc_task_ctx_data(pmu);
- if (!task_ctx_data) {
- kfree(new);
- return ERR_PTR(-ENOMEM);
- }
- }
-
__perf_init_event_pmu_context(new, pmu);

/*
@@ -5080,14 +5020,7 @@ find_get_pmu_context(struct pmu *pmu, struct perf_event_context *ctx,
epc->ctx = ctx;

found_epc:
- if (task_ctx_data && !epc->task_ctx_data) {
- epc->task_ctx_data = task_ctx_data;
- task_ctx_data = NULL;
- ctx->nr_task_data++;
- }
raw_spin_unlock_irq(&ctx->lock);
-
- free_task_ctx_data(pmu, task_ctx_data);
kfree(new);

return epc;
@@ -5103,7 +5036,6 @@ static void free_cpc_rcu(struct rcu_head *head)
struct perf_cpu_pmu_context *cpc =
container_of(head, typeof(*cpc), epc.rcu_head);

- kfree(cpc->epc.task_ctx_data);
kfree(cpc);
}

@@ -5111,7 +5043,6 @@ static void free_epc_rcu(struct rcu_head *head)
{
struct perf_event_pmu_context *epc = container_of(head, typeof(*epc), rcu_head);

- kfree(epc->task_ctx_data);
kfree(epc);
}

@@ -14103,7 +14034,6 @@ inherit_event(struct perf_event *parent_event,
if (is_orphaned_event(parent_event) ||
!atomic_long_inc_not_zero(&parent_event->refcount)) {
mutex_unlock(&parent_event->child_mutex);
- /* task_ctx_data is freed with child_ctx */
free_event(child_event);
return NULL;
}