From: Vlastimil Babka <vbabka@suse.cz>
To: Dave Hansen <dave.hansen@intel.com>, akpm@linux-foundation.org
Cc: hughd@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: documentation: remove hopelessly out-of-date locking doc
Date: Fri, 13 Dec 2013 09:14:54 +0100 [thread overview]
Message-ID: <52AAC1FE.1010409@suse.cz> (raw)
In-Reply-To: <1386703084-24118-1-git-send-email-dave.hansen@intel.com>
On 12/10/2013 08:18 PM, Dave Hansen wrote:
> From: Dave Hansen <dave.hansen@intel.com>
>
> Documentation/vm/locking is a blast from the past. In the entire
> git history, it has had precisely Three modifications. Two of
> those look to be pure renames, and the third was from 2005.
>
> The doc contains such gems as:
>
>> The page_table_lock is grabbed while holding the
>> kernel_lock spinning monitor.
>
>> Page stealers hold kernel_lock to protect against a bunch of
>> races.
>
> Or this which talks about mmap_sem:
>
>> 4. The exception to this rule is expand_stack, which just
>> takes the read lock and the page_table_lock, this is ok
>> because it doesn't really modify fields anybody relies on.
>
> expand_stack() doesn't take any locks any more directly, and the
> mmap_sem acquisition was long ago moved up in to the page fault
> code itself.
>
> It could be argued that we need to rewrite this, but it is
> dangerous to leave it as-is. It will confuse more people than it
> helps.
Heh yeah, when I started few months ago and stumbled upon this doc,
people in the office suggested that I could send a patch that just
deletes it. I wasn't that brave, but I agree nevertheless.
> Signed-off-by: Dave Hansen <dave.hansen@intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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next prev parent reply other threads:[~2013-12-13 8:14 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-10 19:18 [PATCH] mm: documentation: remove hopelessly out-of-date locking doc Dave Hansen
2013-12-13 8:14 ` Vlastimil Babka [this message]
2013-12-13 8:21 ` Wanpeng Li
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