diff options
| author | Paul Jackson <pj@sgi.com> | 2006-05-22 17:56:07 -0700 |
|---|---|---|
| committer | Chris Wright <chrisw@sous-sol.org> | 2006-06-05 10:18:13 -0700 |
| commit | e81ccf5afaf9cff1ed27c29ff96795c146a3d571 (patch) | |
| tree | 74db8a3678d23f171ddced32d75bac5daa679adf /mm/page_alloc.c | |
| parent | 3e211bbe2295ff89490f01d54c6300a8a58fac7c (diff) | |
[PATCH] Cpuset: might sleep checking zones allowed fix
Fix an infrequently encountered 'sleeping function called
from invalid context' in the cpuset hooks in __alloc_pages.
Could sleep while interrupts disabled.
The routine cpuset_zone_allowed() is called by code in
mm/page_alloc.c __alloc_pages() to determine if a zone is
allowed in the current tasks cpuset. This routine can sleep,
for certain GFP_KERNEL allocations, if the zone is on a memory
node not allowed in the current cpuset, but might be allowed
in a parent cpuset.
But we can't sleep in __alloc_pages() if in interrupt, nor
if called for a GFP_ATOMIC request (__GFP_WAIT not set in
gfp_flags).
The rule was intended to be:
Don't call cpuset_zone_allowed() if you can't sleep, unless you
pass in the __GFP_HARDWALL flag set in gfp_flag, which disables
the code that might scan up ancestor cpusets and sleep.
This rule was being violated due to a bogus change made (by myself,
pj) to __alloc_pages() as part of the November 2005 effort to
cleanup its logic.
The bogus change can be seen at:
http://linux.derkeiler.com/Mailing-Lists/Kernel/2005-11/4691.html
[PATCH 01/05] mm fix __alloc_pages cpuset ALLOC_* flags
This was first noticed on a tight memory system, in code that
was disabling interrupts and doing allocation requests with
__GFP_WAIT not set, which resulted in __might_sleep() writing
complaints to the log "Debug: sleeping function called ...",
when the code in cpuset_zone_allowed() tried to take the
callback_sem cpuset semaphore.
Special thanks to Dave Chinner, for figuring this out,
and a tip of the hat to Nick Piggin who warned me of this
back in Nov 2005, before I was ready to listen.
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'mm/page_alloc.c')
| -rw-r--r-- | mm/page_alloc.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 61de2220231e..8b3cde1eb45e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -949,7 +949,8 @@ restart: alloc_flags |= ALLOC_HARDER; if (gfp_mask & __GFP_HIGH) alloc_flags |= ALLOC_HIGH; - alloc_flags |= ALLOC_CPUSET; + if (wait) + alloc_flags |= ALLOC_CPUSET; /* * Go through the zonelist again. Let __GFP_HIGH and allocations |