linux-kernel - Re: [PATCH 2/2] uprobes/core: counter to optimize probe hits.

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Date:	Fri, 23 Mar 2012 13:45:07 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-mm <linux-mm@...ck.org>, Oleg Nesterov <oleg@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 2/2] uprobes/core: counter to optimize probe hits.


* Srikar Dronamraju <srikar@...ux.vnet.ibm.com> wrote:

> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 9ade86e..62d5aeb 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -390,6 +390,7 @@ struct mm_struct {
>  	struct cpumask cpumask_allocation;
>  #endif
>  #ifdef CONFIG_UPROBES
> +	atomic_t mm_uprobes_count;
>  	struct uprobes_xol_area *uprobes_xol_area;
>  #endif

Since mm_types.h includes uprobes.h already it's much better to 
stick this into a 'struct uprobes_state' and thus keep the main 
'struct mm_struct' definition as simple as possible.

Also, your patch titles suck:

  - no proper capitalization like you can observe with previous 
    uprobes commits

  - extra period at the end

  - missing verb from the sentence. Check existing uprobes 
    commits to see the kind of sentences that commit titles are 
    expected to be.

> +	if (!atomic_read(&uprobe_events) || !valid_vma(vma, false))
> +		return;		/* Bail-out */
> +
> +	if (!atomic_read(&vma->vm_mm->mm_uprobes_count))
> +		return;
> +
> +	inode = vma->vm_file->f_mapping->host;
> +	if (!inode)
> +		return;

The 'Bail-out' comment tacked on to one of the returns seems 
entirely superfluous.

> +		if (vaddr >= vma->vm_start && vaddr < vma->vm_end) {
> +
> +			/*

That newline looks superfluous too.

> +	return;
> +}

Please read your own patches more carefully ... this should 
stick out like a sore thumb.

Some of the above comments apply to your other patch as well.

The structure and granularity of the patches looks good 
otherwise.

Thanks,

	Ingo
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