From: Christoph Rohland <cr@sap.com>
To: colpatch@us.ibm.com
Cc: linux-mm@kvack.org, William Lee Irwin III <wli@holomorphy.com>,
"Martin J. Bligh" <mbligh@aracnet.com>
Subject: Re: [question] shm_nattch in sys_shmat?
Date: Mon, 03 Feb 2003 20:48:33 +0100 [thread overview]
Message-ID: <ov4r7lf8mm.fsf@sap.com> (raw)
In-Reply-To: <3E3AFA3A.6050205@us.ibm.com> (Matthew Dobson's message of "Fri, 31 Jan 2003 14:35:38 -0800")
Hi Matthew,
On Fri, 31 Jan 2003, Matthew Dobson wrote:
> sys_shmat, does in fact increment shm_nattch, but only to
> decrement it again a few lines later, as seen in this code
> snippet. Can anyone please explain why this is?
sys_shmat temporarily increases shm_nattch to make sure it's never zero:
> >>> shp->shm_nattch++;
Make sure shm_nattch is greater than zero.
> > user_addr = (void*) do_mmap (file, addr, size, prot,
map the segment which increments shm_nattch in shm_mmap accounting for
the actual mapping
> >>> shp->shm_nattch--;
Correct it again.
Greetings
Christoph
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next prev parent reply other threads:[~2003-02-03 19:48 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-01-31 22:35 Matthew Dobson
2003-02-03 19:48 ` Christoph Rohland [this message]
2003-02-03 23:43 ` Matthew Dobson
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