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From: Robert Watson <rwatson@FreeBSD.org>
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To: Alexander Leidinger <netchild@FreeBSD.org>
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Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/sys/compat/linux linux_misc.c
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On Thu, 17 Aug 2006, Alexander Leidinger wrote:

>  - protect td->td_proc->p_pid with the proc lock in linux_getpid
>    in the amd64 (= non i386) case [1]

Is this necessary?  In principle, td->td_proc is static for a live thread 
bound to a process (i.e., in a system call, which the current thread 
presumable is, as long as td == curthread), p_pid is static for a live process 
that isn't exiting (so in a system call is not generally exiting).  The native 
FreeBSD getpid() only acquires the process lock when following p_pptr, since 
this can change during a system call (i.e., as a result of the parent dying, 
and the child being re-parented to init(8)).

Robert N M Watson
Computer Laboratory
University of Cambridge