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Date:      Thu, 28 Feb 2002 09:57:49 -0500 (EST)
From:      John Baldwin <jhb@FreeBSD.org>
To:        Alfred Perlstein <alfred@FreeBSD.org>
Cc:        cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org
Subject:   RE: cvs commit: src/sys/kern sys_pipe.c src/sys/sys pipe.h
Message-ID:  <XFMail.020228095749.jhb@FreeBSD.org>
In-Reply-To: <200202270735.g1R7ZxR71022@freefall.freebsd.org>

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On 27-Feb-02 Alfred Perlstein wrote:
> alfred      2002/02/26 23:35:59 PST
> 
>   Modified files:
>     sys/kern             sys_pipe.c 
>     sys/sys              pipe.h 
>   Log:
>   First rev at making pipe(2) pipe's MPsafe.
>   
>   Both ends of the pipe share a pool_mutex, this makes allocation
>   and deadlock avoidance easy.
>   
>   Remove some un-needed FILE_LOCK ops while I'm here.
>   
>   There are some issues wrt to select and the f{s,g}etown code that
>   we'll have to deal with, I think we may also need to move the calls
>   to vfs_timestamp outside of the sections covered by PIPE_LOCK.

Looks good, but I have the following questions:

- Why isn't the pipe lock dropped around pipe_destroy_write_buffer() in
  pipe_clone_write_buffer() and the second call in pipe_direct_write() like
  it is in the first call in pipe_direct_write().

- Does pipe_stat() need a lock for any of the fields it reads?

- Can you document some locking notes for struct pipe in pipe.h similar to
  proc.h?

-- 

John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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