On Thu, 13 Mar 2014, Davidlohr Bueso wrote: > On Tue, 2014-03-11 at 18:20 -0400, Sasha Levin wrote: > > On 03/11/2014 05:45 PM, Davidlohr Bueso wrote: > > > On Tue, 2014-03-11 at 17:02 -0400, Sasha Levin wrote: > > >> >On 03/11/2014 04:47 PM, Davidlohr Bueso wrote: > > >>>> > >>Bingo! With the above patch: > > >>>>> > >> > > > >>>>> > >> >[ 243.565794] kernel BUG at mm/vmacache.c:76! > > >>>>> > >> >[ 243.566720] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC > > >>>>> > >> >[ 243.568048] Dumping ftrace buffer: > > >>>>> > >> >[ 243.568740] (ftrace buffer empty) > > >>>>> > >> >[ 243.569481] Modules linked in: > > >>>>> > >> >[ 243.570203] CPU: 10 PID: 10073 Comm: trinity-c332 Tainted: G W 3.14.0-rc5-next-20140307-sasha-00010-g1f812cb-dirty #143 > > >>> > >and this is also part of the DEBUG_PAGEALLOC + trinity combo! I suspect > > >>> > >the root cause it the same as Fengguang's report. > > >> > > > >> >The BUG still happens without DEBUG_PAGEALLOC. > > > Any idea what trinity itself is doing? > > > > > > Could you add the following, I just want to make sure the bug isn't > > > being caused by an overflow: > > > > Not hitting that WARN. > > Sasha, could you please try the following patch: > https://lkml.org/lkml/2014/3/13/312 I was getting the "kernel BUG at mm/vmacache.c:76!" running KSM on mmotm: Oleg's patch (buildable version below) fixes it for me. Hugh --- mmotm/mm/vmacache.c 2014-03-12 18:39:38.008011317 -0700 +++ linux/mm/vmacache.c 2014-03-13 12:21:11.592030813 -0700 @@ -31,15 +31,20 @@ void vmacache_flush_all(struct mm_struct rcu_read_unlock(); } +static bool vmacache_valid_mm(struct mm_struct *mm) +{ + return current->mm == mm && !(current->flags & PF_KTHREAD); +} + void vmacache_update(unsigned long addr, struct vm_area_struct *newvma) { - int idx = VMACACHE_HASH(addr); - current->vmacache[idx] = newvma; + if (vmacache_valid_mm(newvma->vm_mm)) + current->vmacache[VMACACHE_HASH(addr)] = newvma; } static bool vmacache_valid(struct mm_struct *mm) { - struct task_struct *curr = current; + struct task_struct *curr; /* * This task may be accessing a foreign mm via (for example) @@ -47,9 +52,10 @@ static bool vmacache_valid(struct mm_str * task's vmacache pertains to a different mm (ie, its own). There is * nothing we can do here. */ - if (mm != curr->mm) - return false; + if (!vmacache_valid_mm(mm)) + return false; + curr = current; if (mm->vmacache_seqnum != curr->vmacache_seqnum) { /* * First attempt will always be invalid, initialize -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>