perf/core: Don't pass task around when ctx sched in

The current code pass task around for ctx_sched_in(), only
to get perf_cgroup of the task, then update the timestamp
of it and its ancestors and set them to active.

But we can use cpuctx->cgrp to get active perf_cgroup and
its ancestors since cpuctx->cgrp has been set before
ctx_sched_in().

This patch remove the task argument in ctx_sched_in()
and cleanup related code.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220329154523.86438-2-zhouchengming@bytedance.com

Author: Chengming Zhou

kernel/events/core.c

@@ -574,8 +574,7 @@ static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
 			      enum event_type_t event_type);
 
 static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
-			     enum event_type_t event_type,
-			     struct task_struct *task);
+			     enum event_type_t event_type);
 
 static void update_context_time(struct perf_event_context *ctx);
 static u64 perf_event_time(struct perf_event *event);
@@ -801,10 +800,10 @@ static inline void update_cgrp_time_from_event(struct perf_event *event)
 }
 
 static inline void
-perf_cgroup_set_timestamp(struct task_struct *task,
-			  struct perf_event_context *ctx)
+perf_cgroup_set_timestamp(struct perf_cpu_context *cpuctx)
 {
-	struct perf_cgroup *cgrp;
+	struct perf_event_context *ctx = &cpuctx->ctx;
+	struct perf_cgroup *cgrp = cpuctx->cgrp;
 	struct perf_cgroup_info *info;
 	struct cgroup_subsys_state *css;
 
@@ -813,10 +812,10 @@ perf_cgroup_set_timestamp(struct task_struct *task,
 	 * ensure we do not access cgroup data
 	 * unless we have the cgroup pinned (css_get)
 	 */
-	if (!task || !ctx->nr_cgroups)
+	if (!cgrp)
 		return;
 
-	cgrp = perf_cgroup_from_task(task, ctx);
+	WARN_ON_ONCE(!ctx->nr_cgroups);
 
 	for (css = &cgrp->css; css; css = css->parent) {
 		cgrp = container_of(css, struct perf_cgroup, css);
@@ -869,14 +868,14 @@ static void perf_cgroup_switch(struct task_struct *task, int mode)
 			WARN_ON_ONCE(cpuctx->cgrp);
 			/*
 			 * set cgrp before ctxsw in to allow
-			 * event_filter_match() to not have to pass
-			 * task around
+			 * perf_cgroup_set_timestamp() in ctx_sched_in()
+			 * to not have to pass task around
 			 * we pass the cpuctx->ctx to perf_cgroup_from_task()
 			 * because cgorup events are only per-cpu
 			 */
 			cpuctx->cgrp = perf_cgroup_from_task(task,
 							     &cpuctx->ctx);
-			cpu_ctx_sched_in(cpuctx, EVENT_ALL, task);
+			cpu_ctx_sched_in(cpuctx, EVENT_ALL);
 		}
 		perf_pmu_enable(cpuctx->ctx.pmu);
 		perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
@@ -1118,8 +1117,7 @@ static inline int perf_cgroup_connect(pid_t pid, struct perf_event *event,
 }
 
 static inline void
-perf_cgroup_set_timestamp(struct task_struct *task,
-			  struct perf_event_context *ctx)
+perf_cgroup_set_timestamp(struct perf_cpu_context *cpuctx)
 {
 }
 
@@ -2713,8 +2711,7 @@ static void ctx_sched_out(struct perf_event_context *ctx,
 static void
 ctx_sched_in(struct perf_event_context *ctx,
 	     struct perf_cpu_context *cpuctx,
-	     enum event_type_t event_type,
-	     struct task_struct *task);
+	     enum event_type_t event_type);
 
 static void task_ctx_sched_out(struct perf_cpu_context *cpuctx,
 			       struct perf_event_context *ctx,
@@ -2730,15 +2727,14 @@ static void task_ctx_sched_out(struct perf_cpu_context *cpuctx,
 }
 
 static void perf_event_sched_in(struct perf_cpu_context *cpuctx,
-				struct perf_event_context *ctx,
-				struct task_struct *task)
+				struct perf_event_context *ctx)
 {
-	cpu_ctx_sched_in(cpuctx, EVENT_PINNED, task);
+	cpu_ctx_sched_in(cpuctx, EVENT_PINNED);
 	if (ctx)
-		ctx_sched_in(ctx, cpuctx, EVENT_PINNED, task);
-	cpu_ctx_sched_in(cpuctx, EVENT_FLEXIBLE, task);
+		ctx_sched_in(ctx, cpuctx, EVENT_PINNED);
+	cpu_ctx_sched_in(cpuctx, EVENT_FLEXIBLE);
 	if (ctx)
-		ctx_sched_in(ctx, cpuctx, EVENT_FLEXIBLE, task);
+		ctx_sched_in(ctx, cpuctx, EVENT_FLEXIBLE);
 }
 
 /*
@@ -2788,7 +2784,7 @@ static void ctx_resched(struct perf_cpu_context *cpuctx,
 	else if (ctx_event_type & EVENT_PINNED)
 		cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
 
-	perf_event_sched_in(cpuctx, task_ctx, current);
+	perf_event_sched_in(cpuctx, task_ctx);
 	perf_pmu_enable(cpuctx->ctx.pmu);
 }
 
@@ -3011,7 +3007,7 @@ static void __perf_event_enable(struct perf_event *event,
 		return;
 
 	if (!event_filter_match(event)) {
-		ctx_sched_in(ctx, cpuctx, EVENT_TIME, current);
+		ctx_sched_in(ctx, cpuctx, EVENT_TIME);
 		return;
 	}
 
@@ -3020,7 +3016,7 @@ static void __perf_event_enable(struct perf_event *event,
 	 * then don't put it on unless the group is on.
 	 */
 	if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE) {
-		ctx_sched_in(ctx, cpuctx, EVENT_TIME, current);
+		ctx_sched_in(ctx, cpuctx, EVENT_TIME);
 		return;
 	}
 
@@ -3865,8 +3861,7 @@ ctx_flexible_sched_in(struct perf_event_context *ctx,
 static void
 ctx_sched_in(struct perf_event_context *ctx,
 	     struct perf_cpu_context *cpuctx,
-	     enum event_type_t event_type,
-	     struct task_struct *task)
+	     enum event_type_t event_type)
 {
 	int is_active = ctx->is_active;
 
@@ -3878,7 +3873,7 @@ ctx_sched_in(struct perf_event_context *ctx,
 	if (is_active ^ EVENT_TIME) {
 		/* start ctx time */
 		__update_context_time(ctx, false);
-		perf_cgroup_set_timestamp(task, ctx);
+		perf_cgroup_set_timestamp(cpuctx);
 		/*
 		 * CPU-release for the below ->is_active store,
 		 * see __load_acquire() in perf_event_time_now()
@@ -3909,12 +3904,11 @@ ctx_sched_in(struct perf_event_context *ctx,
 }
 
 static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
-			     enum event_type_t event_type,
-			     struct task_struct *task)
+			     enum event_type_t event_type)
 {
 	struct perf_event_context *ctx = &cpuctx->ctx;
 
-	ctx_sched_in(ctx, cpuctx, event_type, task);
+	ctx_sched_in(ctx, cpuctx, event_type);
 }
 
 static void perf_event_context_sched_in(struct perf_event_context *ctx,
@@ -3956,7 +3950,7 @@ static void perf_event_context_sched_in(struct perf_event_context *ctx,
 	 */
 	if (!RB_EMPTY_ROOT(&ctx->pinned_groups.tree))
 		cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
-	perf_event_sched_in(cpuctx, ctx, task);
+	perf_event_sched_in(cpuctx, ctx);
 
 	if (cpuctx->sched_cb_usage && pmu->sched_task)
 		pmu->sched_task(cpuctx->task_ctx, true);
@@ -4267,7 +4261,7 @@ static bool perf_rotate_context(struct perf_cpu_context *cpuctx)
 	if (cpu_event)
 		rotate_ctx(&cpuctx->ctx, cpu_event);
 
-	perf_event_sched_in(cpuctx, task_ctx, current);
+	perf_event_sched_in(cpuctx, task_ctx);
 
 	perf_pmu_enable(cpuctx->ctx.pmu);
 	perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
@@ -4339,7 +4333,7 @@ static void perf_event_enable_on_exec(int ctxn)
 		clone_ctx = unclone_ctx(ctx);
 		ctx_resched(cpuctx, ctx, event_type);
 	} else {
-		ctx_sched_in(ctx, cpuctx, EVENT_TIME, current);
+		ctx_sched_in(ctx, cpuctx, EVENT_TIME);
 	}
 	perf_ctx_unlock(cpuctx, ctx);