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Re: _IO_file_underflow_mmap read call for atime

From: Ulrich Drepper <drepper at redhat dot com>
To: Roland McGrath <roland at frob dot com>
Cc: GNU libc hackers <libc-hacker at sources dot redhat dot com>
Date: Wed, 31 Jul 2002 15:58:00 -0700
Subject: Re: _IO_file_underflow_mmap read call for atime
References: <20020731221647.D8D8B1BA1B@perdition.linnaean.org>

Roland McGrath wrote:

If we assume that the mmap implementations we are using in fact also meet
the stricter criterion of updating st_atime on each read fault, then it is
safe to just use mmap and st_atime will meet the POSIX stdio rules.  I
haven't experimented on Linux, but this is certainly how mmap behaves on
GNU/Hurd.

The Linux code modifies atime when it's mapped. So we'd need a symbol MMAP_ATIME_AT_ACCESS which is defined for Hurd but not for Linux. The read call is only performed when the symbol is not defined.

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Follow-Ups:
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References:
- Re: _IO_file_underflow_mmap read call for atime
  - From: Roland McGrath

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