linux-kernel - Re: [RFC PATCH 4/12 v2] ptrace: introduce the empty "struct ptrace

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Date:	Thu, 28 May 2009 14:15:40 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Christoph Hellwig <hch@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 4/12 v2] ptrace: introduce the empty "struct
	ptrace_context"

> +	task_lock(tsk);
> +	if (likely(!tsk->ptrace_ctx))
> +		tsk->ptrace_ctx = ptrace_ctx;
> +	else
> +		kfree(ptrace_ctx);
> +	task_unlock(tsk);

I don't think it's kosher call kfree with task_lock() held.
The kfree case is a very unlikely path, so it can be:

	task_lock(tsk);
	if (likely(!tsk->ptrace_ctx)) {
		tsk->ptrace_ctx = ptrace_ctx;
		task_unlock(tsk);
		return 0;
	}

	task_unlock(tsk);
	kfree(ptrace_ctx);

Thanks,
Roland
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