* Ingo Molnar <mi...@kernel.org> [2012-12-10 13:44:58]: > Srikar Dronamraju reported that the following assert triggers on > his box: > > kernel BUG at ../kernel/sched/fair.c:2371! > > Call Trace: > [<ffffffff8113cd0e>] __do_numa_page+0xde/0x160 > [<ffffffff8113de9e>] handle_pte_fault+0x32e/0xcd0 > [<ffffffffa01c22c0>] ? drop_large_spte+0x30/0x30 [kvm] > [<ffffffffa01bf215>] ? kvm_set_spte_hva+0x25/0x30 [kvm] > [<ffffffff8113eab9>] handle_mm_fault+0x279/0x760 > [<ffffffff8115c024>] break_ksm+0x74/0xa0 > [<ffffffff8115c222>] break_cow+0xa2/0xb0 > [<ffffffff8115e38c>] ksm_scan_thread+0xb5c/0xd50 > [<ffffffff810771c0>] ? wake_up_bit+0x40/0x40 > [<ffffffff8115d830>] ? run_store+0x340/0x340 > [<ffffffff8107692e>] kthread+0xce/0xe0 > > This means that task_numa_fault() was called for a kernel thread > which has no fault tracking. > > This scenario is actually possible if a kernel thread does > fault processing on behalf of a user-space task - ignore > the page fault in that case. > > Also remove the (now never triggering) assert and robustify > a nearby assert. >
I do confirm that with this change, I dont see the assert anymore. > Reported-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com> > Cc: Linus Torvalds <torva...@linux-foundation.org> > Cc: Andrew Morton <a...@linux-foundation.org> > Cc: Peter Zijlstra <a.p.zijls...@chello.nl> > Cc: Andrea Arcangeli <aarca...@redhat.com> > Cc: Rik van Riel <r...@redhat.com> > Cc: Mel Gorman <mgor...@suse.de> > Cc: Hugh Dickins <hu...@google.com> > Cc: Thomas Gleixner <t...@linutronix.de> > Signed-off-by: Ingo Molnar <mi...@kernel.org> > --- > kernel/sched/fair.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 9d11a8a..61c7a10 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -2351,6 +2351,13 @@ void task_numa_fault(unsigned long addr, int node, int > last_cpupid, int pages, b > int priv; > int idx; > > + /* > + * Kernel threads might not have an mm but might still > + * do fault processing (such as KSM): > + */ > + if (!p->numa_faults) > + return; > + > if (last_cpupid != cpu_pid_to_cpupid(-1, -1)) { > /* Did we access it last time around? */ > if (last_pid == this_pid) { > @@ -2367,8 +2374,8 @@ void task_numa_fault(unsigned long addr, int node, int > last_cpupid, int pages, b > > idx = 2*node + priv; > > - WARN_ON_ONCE(last_cpu == -1 || node == -1); > - BUG_ON(!p->numa_faults); > + if (WARN_ON_ONCE(last_cpu == -1 || node == -1)) > + return; > > p->numa_faults_curr[idx] += pages; > shared_fault_tick(p, node, last_cpu, pages); > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/