linux-kernel - Re: [PATCH 06/10] perf/uprobe: Split uprobe

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Message-Id: <20240710104047.fccde0f9f4332fc974cd9217@kernel.org>
Date: Wed, 10 Jul 2024 10:40:47 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: mingo@...nel.org, andrii@...nel.org, linux-kernel@...r.kernel.org,
 rostedt@...dmis.org, mhiramat@...nel.org, oleg@...hat.com,
 jolsa@...nel.org, clm@...a.com, paulmck@...nel.org
Subject: Re: [PATCH 06/10] perf/uprobe: Split uprobe_unregister()

On Mon, 08 Jul 2024 11:12:47 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> With uprobe_unregister() having grown a synchronize_srcu(), it becomes
> fairly slow to call. Esp. since both users of this API call it in a
> loop.
> 
> Peel off the sync_srcu() and do it once, after the loop.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thanks!

> ---
>  include/linux/uprobes.h     |    8 ++++++--
>  kernel/events/uprobes.c     |    8 ++++++--
>  kernel/trace/bpf_trace.c    |    6 ++++--
>  kernel/trace/trace_uprobe.c |    6 +++++-
>  4 files changed, 21 insertions(+), 7 deletions(-)
> 
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -113,7 +113,8 @@ extern int uprobe_write_opcode(struct ar
>  extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
>  extern int uprobe_register_refctr(struct inode *inode, loff_t offset, loff_t ref_ctr_offset, struct uprobe_consumer *uc);
>  extern int uprobe_apply(struct inode *inode, loff_t offset, struct uprobe_consumer *uc, bool);
> -extern void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
> +extern void uprobe_unregister_nosync(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
> +extern void uprobe_unregister_sync(void);
>  extern int uprobe_mmap(struct vm_area_struct *vma);
>  extern void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end);
>  extern void uprobe_start_dup_mmap(void);
> @@ -163,7 +164,10 @@ uprobe_apply(struct inode *inode, loff_t
>  	return -ENOSYS;
>  }
>  static inline void
> -uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
> +uprobe_unregister_nosync(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
> +{
> +}
> +static inline void uprobes_unregister_sync(void)
>  {
>  }
>  static inline int uprobe_mmap(struct vm_area_struct *vma)
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1126,7 +1126,7 @@ __uprobe_unregister(struct uprobe *uprob
>   * @offset: offset from the start of the file.
>   * @uc: identify which probe if multiple probes are colocated.
>   */
> -void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
> +void uprobe_unregister_nosync(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
>  {
>  	struct uprobe *uprobe;
>  
> @@ -1138,10 +1138,14 @@ void uprobe_unregister(struct inode *ino
>  	__uprobe_unregister(uprobe, uc);
>  	mutex_unlock(&uprobe->register_mutex);
>  	put_uprobe(uprobe);
> +}
> +EXPORT_SYMBOL_GPL(uprobe_unregister_nosync);
>  
> +void uprobe_unregister_sync(void)
> +{
>  	synchronize_srcu(&uprobes_srcu);
>  }
> -EXPORT_SYMBOL_GPL(uprobe_unregister);
> +EXPORT_SYMBOL_GPL(uprobe_unregister_sync);
>  
>  /*
>   * __uprobe_register - register a probe
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -3181,9 +3181,11 @@ static void bpf_uprobe_unregister(struct
>  	u32 i;
>  
>  	for (i = 0; i < cnt; i++) {
> -		uprobe_unregister(d_real_inode(path->dentry), uprobes[i].offset,
> -				  &uprobes[i].consumer);
> +		uprobe_unregister_nosync(d_real_inode(path->dentry), uprobes[i].offset,
> +					 &uprobes[i].consumer);
>  	}
> +	if (cnt)
> +		uprobe_unregister_sync();
>  }
>  
>  static void bpf_uprobe_multi_link_release(struct bpf_link *link)
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -1104,6 +1104,7 @@ static int trace_uprobe_enable(struct tr
>  static void __probe_event_disable(struct trace_probe *tp)
>  {
>  	struct trace_uprobe *tu;
> +	bool sync = false;
>  
>  	tu = container_of(tp, struct trace_uprobe, tp);
>  	WARN_ON(!uprobe_filter_is_empty(tu->tp.event->filter));
> @@ -1112,9 +1113,12 @@ static void __probe_event_disable(struct
>  		if (!tu->inode)
>  			continue;
>  
> -		uprobe_unregister(tu->inode, tu->offset, &tu->consumer);
> +		uprobe_unregister_nosync(tu->inode, tu->offset, &tu->consumer);
> +		sync = true;
>  		tu->inode = NULL;
>  	}
> +	if (sync)
> +		uprobe_unregister_sync();
>  }
>  
>  static int probe_event_enable(struct trace_event_call *call,
> 
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>