linux-kernel - Re: [PATCH 4/4] uprobes: Kill uprobe->copy

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Date:	Thu, 13 Dec 2012 20:00:44 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] uprobes: Kill uprobe->copy_mutex

* Oleg Nesterov <oleg@...hat.com> [2012-11-24 19:02:36]:

> Now that ->register_rwsem is safe under ->mmap_sem we can kill
> ->copy_mutex and abuse down_write(&uprobe->consumer_rwsem).
> 
> This makes prepare_uprobe() even more ugly, but we should kill
> it anyway.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>


Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

> ---
>  kernel/events/uprobes.c |    7 +++----
>  1 files changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 97c3874..1e047f8 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -91,7 +91,6 @@ struct uprobe {
>  	atomic_t		ref;
>  	struct rw_semaphore	register_rwsem;
>  	struct rw_semaphore	consumer_rwsem;
> -	struct mutex		copy_mutex;	/* TODO: kill me and UPROBE_COPY_INSN */
>  	struct list_head	pending_list;
>  	struct uprobe_consumer	*consumers;
>  	struct inode		*inode;		/* Also hold a ref to inode */
> @@ -450,7 +449,6 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)
>  	uprobe->offset = offset;
>  	init_rwsem(&uprobe->register_rwsem);
>  	init_rwsem(&uprobe->consumer_rwsem);
> -	mutex_init(&uprobe->copy_mutex);
>  	/* For now assume that the instruction need not be single-stepped */
>  	__set_bit(UPROBE_SKIP_SSTEP, &uprobe->flags);
> 
> @@ -578,7 +576,8 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
>  	if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
>  		return ret;
> 
> -	mutex_lock(&uprobe->copy_mutex);
> +	/* TODO: move this into _register, until then we abuse this sem. */
> +	down_write(&uprobe->consumer_rwsem);
>  	if (test_bit(UPROBE_COPY_INSN, &uprobe->flags))
>  		goto out;
> 
> @@ -602,7 +601,7 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
>  	set_bit(UPROBE_COPY_INSN, &uprobe->flags);
> 
>   out:
> -	mutex_unlock(&uprobe->copy_mutex);
> +	up_write(&uprobe->consumer_rwsem);
> 
>  	return ret;
>  }
> -- 
> 1.5.5.1
> 

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