Messages in this thread Patch in this message | | | Date | Thu, 18 Jun 2009 17:56:44 +0800 | From | Wu Fengguang <> | Subject | Re: [RFC][PATCH] HWPOISON: only early kill processes who installed SIGBUS handler |
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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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