Re: Redundant uses of might_sleep_if()
From: Andrew Morton (akpm_at_osdl.org)
Date: 01/30/04
- Previous message: Andrew Morton: "Re: 2.6.2-rc2 Interactivity problems with SMP + HT"
- In reply to: ioana alexandrescu: "Redundant uses of might_sleep_if()"
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Date: Fri, 30 Jan 2004 12:18:27 -0800 To: ioana alexandrescu <ioanamitu@yahoo.com>
ioana alexandrescu <ioanamitu@yahoo.com> wrote:
>
> In kernel 2.6.1 it appears that the only necessary
> uses of might_sleep_if()are in __alloc_pages(), and
> perhaps, in cache_alloc_debugcheck_before() (see
> notes).
>
> Other uses of might_sleep_if() appear to be redundant:
>
> Pte_chain_alloc()-->might_sleep_if(), but also
> Pte_chain_alloc-->kmem_cache_alloc
> -->__cache_alloc -->__cache_alloc()
> -->cache_alloc_debugcheck_before()
> -->might_sleep_if()
>
> skb_share_check()-->might_sleep_if(), but also
> skb_share_check()-->skb_clone()
> -->kmem_cache_alloc()[as above]
>
> skb_unshare()-->might_sleep_if(), but also
> skb_unshare()-->skb_copy()
> -->kmem_cache_alloc()[as above]
>
> Other paths through skb_unshare, same result.
>
>
> QUERY: Should these redundant uses be patched out?
Nope.
Take the case of pte_chain_alloc(). Most of the time, it won't call
kmem_cache_alloc() at all. But sometimes it will. But we want to run the
might_sleep() check *every* time someone calls pte_chain_alloc(), not just
some of the times.
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- Previous message: Andrew Morton: "Re: 2.6.2-rc2 Interactivity problems with SMP + HT"
- In reply to: ioana alexandrescu: "Redundant uses of might_sleep_if()"
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