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  1. 17 Oct, 2005 2 commits
    • Herbert Xu's avatar
      [PATCH] list: add missing rcu_dereference on first element · b24d18aa
      Herbert Xu authored 
      It seems that all the list_*_rcu primitives are missing a memory barrier
on the very first dereference.  For example,

#define list_for_each_rcu(pos, head) \
	for (pos = (head)->next; prefetch(pos->next), pos != (head); \
		pos = rcu_dereference(pos->next))

It will go something like:

	pos = (head)->next

	prefetch(pos->next)

	pos != (head)

	do stuff

We're missing a barrier here.

	pos = rcu_dereference(pos->next)

		fetch pos->next

		barrier given by rcu_dereference(pos->next)

		store pos

Without the missing barrier, the pos->next value may turn out to be stale.
In fact, if "do stuff" were also dereferencing pos and relying on
list_for_each_rcu to provide the barrier then it may also break.

So here is a patch to make sure that we have a barrier for the first
element in the list.
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Acked-by: default avatar"Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      b24d18aa
    • Linus Torvalds's avatar
      Fix memory ordering bug in page reclaim · 3d80636a
      Linus Torvalds authored 
      As noticed by Nick Piggin, we need to make sure that we check the page
count before we check for PageDirty, since the dirty check is only valid
if the count implies that we're the only possible ones holding the page.

We always did do this, but the code needs a read-memory-barrier to make
sure that the orderign is also honored by the CPU.

(The writer side is ordered due to the atomic decrement and test on the
page count, see the discussion on linux-kernel)
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      3d80636a
  3. 16 Oct, 2005 1 commit
    • Al Viro's avatar
      [PATCH]: highest_possible_processor_id() has to be a macro · 688ce17b
      Al Viro authored 
      	... otherwise, things like alpha and sparc64 break and break
badly.  They define cpu_possible_map to something else in smp.h
*AFTER* having included cpumask.h.

	If that puppy is a macro, expansion will happen at the actual
caller, when we'd already seen #define cpu_possible_map ... and we will
get the right thing used.

	As an inline helper it will be tokenized before we get to that
define and that's it; no matter what we define later, it won't affect
anything.  We get modules with dependency on cpu_possible_map instead
of the right symbol (phys_cpu_present_map in case of sparc64), or outright
link errors if they are built-in.
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      688ce17b
  5. 15 Oct, 2005 20 commits
  7. 14 Oct, 2005 11 commits
  9. 13 Oct, 2005 6 commits
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