linux-kernel - [PATCH v3 43/57] perf: Simplify perf_sw

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Message-ID: <20230612093540.638818161@infradead.org>
Date:   Mon, 12 Jun 2023 11:07:56 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     torvalds@...ux-foundation.org, keescook@...omium.org,
        gregkh@...uxfoundation.org, pbonzini@...hat.com
Cc:     masahiroy@...nel.org, nathan@...nel.org, ndesaulniers@...gle.com,
        nicolas@...sle.eu, catalin.marinas@....com, will@...nel.org,
        vkoul@...nel.org, trix@...hat.com, ojeda@...nel.org,
        peterz@...radead.org, mingo@...hat.com, longman@...hat.com,
        boqun.feng@...il.com, dennis@...nel.org, tj@...nel.org,
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        luc.vanoostenryck@...il.com
Subject: [PATCH v3 43/57] perf: Simplify perf_sw_event()


Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/events/core.c |   37 ++++++++++++-------------------------
 1 file changed, 12 insertions(+), 25 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9701,17 +9701,15 @@ static void do_perf_sw_event(enum perf_t
 	struct perf_event *event;
 	struct hlist_head *head;
 
-	rcu_read_lock();
+	guard(rcu)();
 	head = find_swevent_head_rcu(swhash, type, event_id);
 	if (!head)
-		goto end;
+		return;
 
 	hlist_for_each_entry_rcu(event, head, hlist_entry) {
 		if (perf_swevent_match(event, type, event_id, data, regs))
 			perf_swevent_event(event, nr, data, regs);
 	}
-end:
-	rcu_read_unlock();
 }
 
 DEFINE_PER_CPU(struct pt_regs, __perf_regs[4]);
@@ -9746,16 +9744,13 @@ void __perf_sw_event(u32 event_id, u64 n
 {
 	int rctx;
 
-	preempt_disable_notrace();
+	guard(preempt_notrace)();
 	rctx = perf_swevent_get_recursion_context();
 	if (unlikely(rctx < 0))
-		goto fail;
+		return;
 
 	___perf_sw_event(event_id, nr, regs, addr);
-
 	perf_swevent_put_recursion_context(rctx);
-fail:
-	preempt_enable_notrace();
 }
 
 static void perf_swevent_read(struct perf_event *event)
@@ -9844,21 +9839,17 @@ static int swevent_hlist_get_cpu(int cpu
 	struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);
 	int err = 0;
 
-	mutex_lock(&swhash->hlist_mutex);
+	guard(mutex)(&swhash->hlist_mutex);
 	if (!swevent_hlist_deref(swhash) &&
 	    cpumask_test_cpu(cpu, perf_online_mask)) {
 		struct swevent_hlist *hlist;
 
 		hlist = kzalloc(sizeof(*hlist), GFP_KERNEL);
-		if (!hlist) {
-			err = -ENOMEM;
-			goto exit;
-		}
+		if (!hlist)
+			return -ENOMEM;
 		rcu_assign_pointer(swhash->swevent_hlist, hlist);
 	}
 	swhash->hlist_refcount++;
-exit:
-	mutex_unlock(&swhash->hlist_mutex);
 
 	return err;
 }
@@ -10115,16 +10106,12 @@ void perf_tp_event(u16 event_type, u64 c
 	if (task && task != current) {
 		struct perf_event_context *ctx;
 
-		rcu_read_lock();
+		guard(rcu)();
 		ctx = rcu_dereference(task->perf_event_ctxp);
-		if (!ctx)
-			goto unlock;
-
-		raw_spin_lock(&ctx->lock);
-		perf_tp_event_target_task(count, record, regs, &data, ctx);
-		raw_spin_unlock(&ctx->lock);
-unlock:
-		rcu_read_unlock();
+		if (ctx) {
+			guard(raw_spinlock)(&ctx->lock);
+			perf_tp_event_target_task(count, record, regs, &data, ctx);
+		}
 	}
 
 	perf_swevent_put_recursion_context(rctx);