FYI, there is an obvious bug in cpusets in 2.6.15-rcX:
cpuset_excl_nodes_overlap() may sleep (as it takes semaphore), but is
called from atomic context - select_bad_process() under tasklist_lock.
BUG. Found by Denis Lunev.
Sorry for not responding sooner - I was off the air for a week.
Thanks for finding and reporting this.
Apparently, from KUROSAWA Takahiro's report, this bug was also in
2.6.14. My initial reading of the code in 2.6.14 and 2.6.15-* agrees,
and finds that this bug was present since the cpuset_excl_nodes_overlap
call was added, Sept 8, 2005 (in Linus's tree.)
the same actually applies to cpuset_zone_allowed() which is called e.g.
from __alloc_pages()->get_page_from_freelist() and doesn't check for
GPF_NOATOMIC anyhow...
I don't think so. Please read the comments in kernel/cpuset.c above
the routine cpuset_zone_allowed(). Either that routine is called with
the __GFP_HARDWALL flag set, so returns before it gets to the semaphore
call, or it is not called at all, due to the check for ATOMIC (!wait)
in mm/page_alloc.c.
I don't see any bugs like this, in the cpuset_zone_allowed code path.
this piece of code in __alloc_pages():
if (((p->flags & PF_MEMALLOC) ||
unlikely(test_thread_flag(TIF_MEMDIE)))
&& !in_interrupt()) {
if (!(gfp_mask & __GFP_NOMEMALLOC)) {
nofail_alloc:
/* go through the zonelist yet again, ignoring
mins */
page = get_page_from_freelist(gfp_mask, order,
zonelist,
ALLOC_NO_WATERMARKS|ALLOC_CPUSET);
ALLOC_CPUSET is specified, gfp_mask can be GFP_ATOMIC still and no
__GFP_HARDWALL. Am I wrong?
Kirill
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