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Date: Thu, 18 Jun 2009 17:56:44 +0800
From: Wu Fengguang <fengguang.wu@...el.com>
To: Nick Piggin <npiggin@...e.de>
Cc: Andi Kleen <andi@...stfloor.org>,
Balbir Singh <balbir@...ux.vnet.ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
Mel Gorman <mel@....ul.ie>,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Hugh Dickins <hugh.dickins@...cali.co.uk>,
"riel@...hat.com" <riel@...hat.com>,
"chris.mason@...cle.com" <chris.mason@...cle.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [RFC][PATCH] HWPOISON: only early kill processes who installed
SIGBUS handler
On Wed, Jun 17, 2009 at 04:04:04PM +0800, Nick Piggin wrote:
> On Wed, Jun 17, 2009 at 02:37:02PM +0800, Wu Fengguang wrote:
> > On Mon, Jun 15, 2009 at 10:22:25PM +0800, Wu Fengguang wrote:
> > > On Mon, Jun 15, 2009 at 08:25:28PM +0800, Nick Piggin wrote:
> > > > On Mon, Jun 15, 2009 at 08:10:01PM +0800, Wu Fengguang wrote:
> > > > > On Mon, Jun 15, 2009 at 03:19:07PM +0800, Nick Piggin wrote:
> > > > > > > For KVM you need early kill, for the others it remains to be seen.
> > > > > >
> > > > > > Right. It's almost like you need to do a per-process thing, and
> > > > > > those that can handle things (such as the new SIGBUS or the new
> > > > > > EIO) could get those, and others could be killed.
> > > > >
> > > > > To send early SIGBUS kills to processes who has called
> > > > > sigaction(SIGBUS, ...)? KVM will sure do that. For other apps we
> > > > > don't mind they can understand that signal at all.
> > > >
> > > > For apps that hook into SIGBUS for some other means and
> > >
> > > Yes I was referring to the sigaction(SIGBUS) apps, others will
> > > be late killed anyway.
> > >
> > > > do not understand the new type of SIGBUS signal? What about
> > > > those?
> > >
> > > We introduced two new SIGBUS codes:
> > > BUS_MCEERR_AO=5 for early kill
> > > BUS_MCEERR_AR=4 for late kill
> > > I'd assume a legacy application will handle them in the same way (both
> > > are unexpected code to the application).
> > >
> > > We don't care whether the application can be killed by BUS_MCEERR_AO
> > > or BUS_MCEERR_AR depending on its SIGBUS handler implementation.
> > > But (in the rare case) if the handler
> > > - refused to die on BUS_MCEERR_AR, it may create a busy loop and
> > > flooding of SIGBUS signals, which is a bug of the application.
> > > BUS_MCEERR_AO is one time and won't lead to busy loops.
> > > - does something that hurts itself (ie. data safety) on BUS_MCEERR_AO,
> > > it may well hurt the same way on BUS_MCEERR_AR. The latter one is
> > > unavoidable, so the application must be fixed anyway.
> >
> > This patch materializes the automatically early kill idea.
> > It aims to remove the vm.memory_failure_ealy_kill sysctl parameter.
> >
> > This is mainly a policy change, please comment.
>
> Well then you can still early-kill random apps that did not
> want it, and you may still cause problems if its sigbus
> handler does something nontrivial.
>
> Can you use a prctl or something so it can expclitly
> register interest in this?
OK, this patch allows one to request early kill by calling
prctl(PR_MEMORY_FAILURE_EARLY_KILL, 1, ...).
Now either app or admin can choose to enable/disable early kill on
a per-process basis. But still, an admin won't be able to change the
behavior of an application who calls prctl() to set the option by itself.
Thanks,
Fengguang
---
include/linux/prctl.h | 6 ++++++
include/linux/sched.h | 1 +
kernel/sys.c | 6 ++++++
mm/memory-failure.c | 12 ++++++++++--
4 files changed, 23 insertions(+), 2 deletions(-)
--- sound-2.6.orig/include/linux/prctl.h
+++ sound-2.6/include/linux/prctl.h
@@ -88,4 +88,10 @@
#define PR_TASK_PERF_COUNTERS_DISABLE 31
#define PR_TASK_PERF_COUNTERS_ENABLE 32
+/*
+ * Send early SIGBUS.BUS_MCEERR_AO notification on memory corruption?
+ * Useful for KVM and mission critical apps.
+ */
+#define PR_MEMORY_FAILURE_EARLY_KILL 33
+
#endif /* _LINUX_PRCTL_H */
--- sound-2.6.orig/include/linux/sched.h
+++ sound-2.6/include/linux/sched.h
@@ -1666,6 +1666,7 @@ extern cputime_t task_gtime(struct task_
#define PF_MEMALLOC 0x00000800 /* Allocating memory */
#define PF_FLUSHER 0x00001000 /* responsible for disk writeback */
#define PF_USED_MATH 0x00002000 /* if unset the fpu must be initialized before use */
+#define PF_EARLY_KILL 0x00004000 /* early kill me on memory failure */
#define PF_NOFREEZE 0x00008000 /* this thread should not be frozen */
#define PF_FROZEN 0x00010000 /* frozen for system suspend */
#define PF_FSTRANS 0x00020000 /* inside a filesystem transaction */
--- sound-2.6.orig/kernel/sys.c
+++ sound-2.6/kernel/sys.c
@@ -1545,6 +1545,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsi
current->timer_slack_ns = arg2;
error = 0;
break;
+ case PR_MEMORY_FAILURE_EARLY_KILL:
+ if (arg2)
+ me->flags |= PF_EARLY_KILL;
+ else
+ me->flags &= ~PF_EARLY_KILL;
+ break;
default:
error = -EINVAL;
break;
--- sound-2.6.orig/mm/memory-failure.c
+++ sound-2.6/mm/memory-failure.c
@@ -205,6 +205,14 @@ static void kill_procs_ao(struct list_he
}
}
+static bool task_early_kill_elegible(struct task_struct *tsk)
+{
+ if (!tsk->mm)
+ return false;
+
+ return tsk->flags & PF_EARLY_KILL;
+}
+
/*
* Collect processes when the error hit an anonymous page.
*/
@@ -222,7 +230,7 @@ static void collect_procs_anon(struct pa
goto out;
for_each_process (tsk) {
- if (!tsk->mm)
+ if (!task_early_kill_elegible(tsk))
continue;
list_for_each_entry (vma, &av->head, anon_vma_node) {
if (!page_mapped_in_vma(page, vma))
@@ -262,7 +270,7 @@ static void collect_procs_file(struct pa
for_each_process(tsk) {
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
- if (!tsk->mm)
+ if (!task_early_kill_elegible(tsk))
continue;
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
--
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