The patch titled
Cpuset: might sleep checking zones allowed fix
has been added to the -mm tree. Its filename is
cpuset-might-sleep-checking-zones-allowed-fix.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
From: Paul Jackson <pj@xxxxxxx>
Fix a couple of 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 in a couple of places, due to a bogus change
made (by myself, pj) to __alloc_pages() as part of the November 2005 effort
to cleanup its logic, and also due to a later fix to constrain which swap
daemons were awoken.
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.
We haven't seen a system hang on this 'might_sleep' yet, but we are at
decent risk of seeing it fairly soon, especially since the additional
cpuset_zone_allowed() check was added, conditioning wakeup_kswapd(), in
March 2006.
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@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
mm/page_alloc.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
diff -puN mm/page_alloc.c~cpuset-might-sleep-checking-zones-allowed-fix mm/page_alloc.c
--- devel/mm/page_alloc.c~cpuset-might-sleep-checking-zones-allowed-fix 2006-05-17 22:26:20.000000000 -0700
+++ devel-akpm/mm/page_alloc.c 2006-05-17 22:26:20.000000000 -0700
@@ -957,7 +957,7 @@ restart:
goto got_pg;
do {
- if (cpuset_zone_allowed(*z, gfp_mask))
+ if (cpuset_zone_allowed(*z, gfp_mask|__GFP_HARDWALL))
wakeup_kswapd(*z, order);
} while (*(++z));
@@ -976,7 +976,8 @@ 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
_
Patches currently in -mm which might be from pj@xxxxxxx are
cpuset-might-sleep-checking-zones-allowed-fix.patch
proc-dont-lock-task_structs-indefinitely.patch
proc-dont-lock-task_structs-indefinitely-task_mmu-small-fixes.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
