diff mbox series

[v3,26/57] perf: Simplify event_function*()

Message ID 20230612093539.371360635@infradead.org (mailing list archive)
State New, archived
Headers show
Series Scope-based Resource Management | expand

Commit Message

Peter Zijlstra June 12, 2023, 9:07 a.m. UTC 
Use guards to reduce gotos and simplify control flow.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/events/core.c |   39 ++++++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 13 deletions(-)

Comments

Dan Carpenter June 12, 2023, 2:46 p.m. UTC | #1 
On Mon, Jun 12, 2023 at 11:07:39AM +0200, Peter Zijlstra wrote:
> @@ -224,17 +243,15 @@ static int event_function(void *info)
>  	int ret = 0;
>  
>  	lockdep_assert_irqs_disabled();
> +	guard(perf_ctx_lock)(cpuctx, task_ctx);
>  
> -	perf_ctx_lock(cpuctx, task_ctx);
>  	/*
>  	 * Since we do the IPI call without holding ctx->lock things can have
>  	 * changed, double check we hit the task we set out to hit.
>  	 */
>  	if (ctx->task) {
> -		if (ctx->task != current) {
> -			ret = -ESRCH;
> -			goto unlock;
> -		}
> +		if (ctx->task != current)
> +			return -ESRCH;
>  
>  		/*
>  		 * We only use event_function_call() on established contexts,
> @@ -254,8 +271,6 @@ static int event_function(void *info)
>  	}
>  
>  	efs->func(event, cpuctx, ctx, efs->data);
> -unlock:
> -	perf_ctx_unlock(cpuctx, task_ctx);
>  
>  	return ret;


We can change this to a return 0; and get rid of the "ret" variable.

regards,
dan carpenter
Peter Zijlstra June 12, 2023, 2:58 p.m. UTC | #2 
On Mon, Jun 12, 2023 at 05:46:47PM +0300, Dan Carpenter wrote:
> On Mon, Jun 12, 2023 at 11:07:39AM +0200, Peter Zijlstra wrote:
> > @@ -224,17 +243,15 @@ static int event_function(void *info)
> >  	int ret = 0;
> >  
> >  	lockdep_assert_irqs_disabled();
> > +	guard(perf_ctx_lock)(cpuctx, task_ctx);
> >  
> > -	perf_ctx_lock(cpuctx, task_ctx);
> >  	/*
> >  	 * Since we do the IPI call without holding ctx->lock things can have
> >  	 * changed, double check we hit the task we set out to hit.
> >  	 */
> >  	if (ctx->task) {
> > -		if (ctx->task != current) {
> > -			ret = -ESRCH;
> > -			goto unlock;
> > -		}
> > +		if (ctx->task != current)
> > +			return -ESRCH;
> >  
> >  		/*
> >  		 * We only use event_function_call() on established contexts,
> > @@ -254,8 +271,6 @@ static int event_function(void *info)
> >  	}
> >  
> >  	efs->func(event, cpuctx, ctx, efs->data);
> > -unlock:
> > -	perf_ctx_unlock(cpuctx, task_ctx);
> >  
> >  	return ret;
> 
> 
> We can change this to a return 0; and get rid of the "ret" variable.

This and the previous one, done!
Namhyung Kim June 13, 2023, 5:56 a.m. UTC | #3 
Hi Peter,

On Mon, Jun 12, 2023 at 2:39 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> Use guards to reduce gotos and simplify control flow.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
>  kernel/events/core.c |   39 ++++++++++++++++++++++++++-------------
>  1 file changed, 26 insertions(+), 13 deletions(-)
>
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -214,6 +214,25 @@ struct event_function_struct {
>         void *data;
>  };
>
> +typedef struct {
> +       struct perf_cpu_context *cpuctx;
> +       struct perf_event_context *ctx;
> +} class_perf_ctx_lock_t;
> +
> +static inline void class_perf_ctx_lock_destructor(class_perf_ctx_lock_t *_T)
> +{
> +       if (_T->cpuctx)
> +               perf_ctx_unlock(_T->cpuctx, _T->ctx);

Shouldn't it be called unconditionally?

Thanks,
Namhyung

> +}
> +
> +static inline class_perf_ctx_lock_t
> +class_perf_ctx_lock_constructor(struct perf_cpu_context *cpuctx,
> +                               struct perf_event_context *ctx)
> +{
> +       perf_ctx_lock(cpuctx, ctx);
> +       return (class_perf_ctx_lock_t){ cpuctx, ctx };
> +}
> +
>  static int event_function(void *info)
>  {
>         struct event_function_struct *efs = info;
> @@ -224,17 +243,15 @@ static int event_function(void *info)
>         int ret = 0;
>
>         lockdep_assert_irqs_disabled();
> +       guard(perf_ctx_lock)(cpuctx, task_ctx);
>
> -       perf_ctx_lock(cpuctx, task_ctx);
>         /*
>          * Since we do the IPI call without holding ctx->lock things can have
>          * changed, double check we hit the task we set out to hit.
>          */
>         if (ctx->task) {
> -               if (ctx->task != current) {
> -                       ret = -ESRCH;
> -                       goto unlock;
> -               }
> +               if (ctx->task != current)
> +                       return -ESRCH;
>
>                 /*
>                  * We only use event_function_call() on established contexts,
> @@ -254,8 +271,6 @@ static int event_function(void *info)
>         }
>
>         efs->func(event, cpuctx, ctx, efs->data);
> -unlock:
> -       perf_ctx_unlock(cpuctx, task_ctx);
>
>         return ret;
>  }
> @@ -329,11 +344,11 @@ static void event_function_local(struct
>                 task_ctx = ctx;
>         }
>
> -       perf_ctx_lock(cpuctx, task_ctx);
> +       guard(perf_ctx_lock)(cpuctx, task_ctx);
>
>         task = ctx->task;
>         if (task == TASK_TOMBSTONE)
> -               goto unlock;
> +               return;
>
>         if (task) {
>                 /*
> @@ -343,18 +358,16 @@ static void event_function_local(struct
>                  */
>                 if (ctx->is_active) {
>                         if (WARN_ON_ONCE(task != current))
> -                               goto unlock;
> +                               return;
>
>                         if (WARN_ON_ONCE(cpuctx->task_ctx != ctx))
> -                               goto unlock;
> +                               return;
>                 }
>         } else {
>                 WARN_ON_ONCE(&cpuctx->ctx != ctx);
>         }
>
>         func(event, cpuctx, ctx, data);
> -unlock:
> -       perf_ctx_unlock(cpuctx, task_ctx);
>  }
>
>  #define PERF_FLAG_ALL (PERF_FLAG_FD_NO_GROUP |\
>
>
Peter Zijlstra June 13, 2023, 7:39 a.m. UTC | #4 
On Mon, Jun 12, 2023 at 10:56:06PM -0700, Namhyung Kim wrote:
> Hi Peter,
> 
> On Mon, Jun 12, 2023 at 2:39 AM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > Use guards to reduce gotos and simplify control flow.
> >
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > ---
> >  kernel/events/core.c |   39 ++++++++++++++++++++++++++-------------
> >  1 file changed, 26 insertions(+), 13 deletions(-)
> >
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -214,6 +214,25 @@ struct event_function_struct {
> >         void *data;
> >  };
> >
> > +typedef struct {
> > +       struct perf_cpu_context *cpuctx;
> > +       struct perf_event_context *ctx;
> > +} class_perf_ctx_lock_t;
> > +
> > +static inline void class_perf_ctx_lock_destructor(class_perf_ctx_lock_t *_T)
> > +{
> > +       if (_T->cpuctx)
> > +               perf_ctx_unlock(_T->cpuctx, _T->ctx);
> 
> Shouldn't it be called unconditionally?

In all surviving cases it will be, so yeah, I can remove that condition.
diff mbox series

Patch

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -214,6 +214,25 @@  struct event_function_struct {
 	void *data;
 };
 
+typedef struct {
+	struct perf_cpu_context *cpuctx;
+	struct perf_event_context *ctx;
+} class_perf_ctx_lock_t;
+
+static inline void class_perf_ctx_lock_destructor(class_perf_ctx_lock_t *_T)
+{
+	if (_T->cpuctx)
+		perf_ctx_unlock(_T->cpuctx, _T->ctx);
+}
+
+static inline class_perf_ctx_lock_t
+class_perf_ctx_lock_constructor(struct perf_cpu_context *cpuctx,
+				struct perf_event_context *ctx)
+{
+	perf_ctx_lock(cpuctx, ctx);
+	return (class_perf_ctx_lock_t){ cpuctx, ctx };
+}
+
 static int event_function(void *info)
 {
 	struct event_function_struct *efs = info;
@@ -224,17 +243,15 @@  static int event_function(void *info)
 	int ret = 0;
 
 	lockdep_assert_irqs_disabled();
+	guard(perf_ctx_lock)(cpuctx, task_ctx);
 
-	perf_ctx_lock(cpuctx, task_ctx);
 	/*
 	 * Since we do the IPI call without holding ctx->lock things can have
 	 * changed, double check we hit the task we set out to hit.
 	 */
 	if (ctx->task) {
-		if (ctx->task != current) {
-			ret = -ESRCH;
-			goto unlock;
-		}
+		if (ctx->task != current)
+			return -ESRCH;
 
 		/*
 		 * We only use event_function_call() on established contexts,
@@ -254,8 +271,6 @@  static int event_function(void *info)
 	}
 
 	efs->func(event, cpuctx, ctx, efs->data);
-unlock:
-	perf_ctx_unlock(cpuctx, task_ctx);
 
 	return ret;
 }
@@ -329,11 +344,11 @@  static void event_function_local(struct
 		task_ctx = ctx;
 	}
 
-	perf_ctx_lock(cpuctx, task_ctx);
+	guard(perf_ctx_lock)(cpuctx, task_ctx);
 
 	task = ctx->task;
 	if (task == TASK_TOMBSTONE)
-		goto unlock;
+		return;
 
 	if (task) {
 		/*
@@ -343,18 +358,16 @@  static void event_function_local(struct
 		 */
 		if (ctx->is_active) {
 			if (WARN_ON_ONCE(task != current))
-				goto unlock;
+				return;
 
 			if (WARN_ON_ONCE(cpuctx->task_ctx != ctx))
-				goto unlock;
+				return;
 		}
 	} else {
 		WARN_ON_ONCE(&cpuctx->ctx != ctx);
 	}
 
 	func(event, cpuctx, ctx, data);
-unlock:
-	perf_ctx_unlock(cpuctx, task_ctx);
 }
 
 #define PERF_FLAG_ALL (PERF_FLAG_FD_NO_GROUP |\