Messages in this thread Patch in this message | | | Date | Tue, 01 Sep 2009 21:51:03 +0900 | From | Tejun Heo <> | Subject | [GIT PULL] percpu fixes for 2.6.31-rc8 |
| |
Hello, Linus.
Please consider pulling from the following percpu fixes tree.
git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu.git for-linus
This branch contains one critical fix for sparc64. Dynamic percpu allocator in 2.6.31 tree still assumed that cpu0 always exists which is not true on certain sparc64 machines. This leads to malfunction in the allocator leading to unmapping of used area and then oops. This was reported in the following thread.
http://thread.gmane.org/gmane.linux.ports.sparc/12138
Using raw_smp_processor_id() instead of 0 in two places fixes the problem. Devel branch had both (sans raw_ prefix) but the first one was no longer necessary and dropped. Both chunk->page[] array and vmalloc area back pointing which the fix touches are always done for all possible cpus in unison and what changes is percpu now uses raw_smp_processor_id() to use any possible one of the cpus instead of explicit 0. Given that the changes have been in linux-next for some time now, I believe these changes to be quite safe.
Thanks. --- Tejun Heo (1): percpu: don't assume existence of cpu0
mm/percpu.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/mm/percpu.c b/mm/percpu.c index 5fe3784..3311c89 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -197,7 +197,12 @@ static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk, static bool pcpu_chunk_page_occupied(struct pcpu_chunk *chunk, int page_idx) { - return *pcpu_chunk_pagep(chunk, 0, page_idx) != NULL; + /* + * Any possible cpu id can be used here, so there's no need to + * worry about preemption or cpu hotplug. + */ + return *pcpu_chunk_pagep(chunk, raw_smp_processor_id(), + page_idx) != NULL; }
/* set the pointer to a chunk in a page struct */ @@ -297,6 +302,14 @@ static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr) return pcpu_first_chunk; }
+ /* + * The address is relative to unit0 which might be unused and + * thus unmapped. Offset the address to the unit space of the + * current processor before looking it up in the vmalloc + * space. Note that any possible cpu id can be used here, so + * there's no need to worry about preemption or cpu hotplug. + */ + addr += raw_smp_processor_id() * pcpu_unit_size; return pcpu_get_page_chunk(vmalloc_to_page(addr)); }
| |