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Subject: Re: [PATCH v3 0/10] Uprobes v3
From: Peter Zijlstra <peterz@infradead.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>, Masami Hiramatsu <mhiramat@redhat.com>,
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Date: Tue, 11 May 2010 22:59:45 +0200
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On Thu, 2010-05-06 at 23:31 +0530, Srikar Dronamraju wrote:
>   - Addressed comments from Oleg, including removal of interrupt context
>     handlers, reverting background page replacement in favour of
>     access_process_vm(). 


> +static int write_opcode(struct task_struct *tsk, unsigned long vaddr,
> +                                               user_bkpt_opcode_t opcode)
> +{
> +       int ret;
> +
> +       if (!tsk)
> +               return -EINVAL;
> +
> +       ret = access_process_vm(tsk, vaddr, &opcode, user_bkpt_opcode_sz, 1);
> +       return (ret == user_bkpt_opcode_sz ? 0 : -EFAULT);
> +}

Why!

That's not not the atomic sequence outlined.