From c22ab332902333f83766017478c1ef6607ace681 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Mon, 5 Mar 2012 14:59:10 -0800 Subject: kmsg_dump: don't run on non-error paths by default Since commit 04c6862c055f ("kmsg_dump: add kmsg_dump() calls to the reboot, halt, poweroff and emergency_restart paths"), kmsg_dump() gets run on normal paths including poweroff and reboot. This is less than ideal given pstore implementations that can only represent single backtraces, since a reboot may overwrite a stored oops before it's been picked up by userspace. In addition, some pstore backends may have low performance and provide a significant delay in reboot as a result. This patch adds a printk.always_kmsg_dump kernel parameter (which can also be changed from userspace). Without it, the code will only be run on failure paths rather than on normal paths. The option can be enabled in environments where there's a desire to attempt to audit whether or not a reboot was cleanly requested or not. Signed-off-by: Matthew Garrett Acked-by: Seiji Aguchi Cc: Seiji Aguchi Cc: David Woodhouse Cc: Marco Stornelli Cc: Artem Bityutskiy Cc: KOSAKI Motohiro Cc: Vivek Goyal Cc: Don Zickus Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kmsg_dump.h | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h index fee66317e071..35f7237ec972 100644 --- a/include/linux/kmsg_dump.h +++ b/include/linux/kmsg_dump.h @@ -15,13 +15,18 @@ #include #include +/* + * Keep this list arranged in rough order of priority. Anything listed after + * KMSG_DUMP_OOPS will not be logged by default unless printk.always_kmsg_dump + * is passed to the kernel. + */ enum kmsg_dump_reason { - KMSG_DUMP_OOPS, KMSG_DUMP_PANIC, + KMSG_DUMP_OOPS, + KMSG_DUMP_EMERG, KMSG_DUMP_RESTART, KMSG_DUMP_HALT, KMSG_DUMP_POWEROFF, - KMSG_DUMP_EMERG, }; /** -- cgit v1.2.3 From c415c3b47ea2754659d915cca387a20999044163 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 5 Mar 2012 14:59:13 -0800 Subject: vfork: introduce complete_vfork_done() No functional changes. Move the clear-and-complete-vfork_done code into the new trivial helper, complete_vfork_done(). Signed-off-by: Oleg Nesterov Acked-by: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sched.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/linux/sched.h b/include/linux/sched.h index 7d379a6bfd88..1b25a37f2aee 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2291,6 +2291,7 @@ extern int do_execve(const char *, const char __user * const __user *, const char __user * const __user *, struct pt_regs *); extern long do_fork(unsigned long, unsigned long, struct pt_regs *, unsigned long, int __user *, int __user *); +extern void complete_vfork_done(struct task_struct *tsk); struct task_struct *fork_idle(int); extern void set_task_comm(struct task_struct *tsk, char *from); -- cgit v1.2.3 From d68b46fe16ad59b3a5f51ec73daaa5dc06753798 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 5 Mar 2012 14:59:13 -0800 Subject: vfork: make it killable Make vfork() killable. Change do_fork(CLONE_VFORK) to do wait_for_completion_killable(). If it fails we do not return to the user-mode and never touch the memory shared with our child. However, in this case we should clear child->vfork_done before return, we use task_lock() in do_fork()->wait_for_vfork_done() and complete_vfork_done() to serialize with each other. Note: now that we use task_lock() we don't really need completion, we could turn task->vfork_done into "task_struct *wake_up_me" but this needs some complications. NOTE: this and the next patches do not affect in-kernel users of CLONE_VFORK, kernel threads run with all signals ignored including SIGKILL/SIGSTOP. However this is obviously the user-visible change. Not only a fatal signal can kill the vforking parent, a sub-thread can do execve or exit_group() and kill the thread sleeping in vfork(). Signed-off-by: Oleg Nesterov Acked-by: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sched.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/sched.h b/include/linux/sched.h index 1b25a37f2aee..b6467711f12e 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2372,7 +2372,7 @@ static inline int thread_group_empty(struct task_struct *p) * Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring * subscriptions and synchronises with wait4(). Also used in procfs. Also * pins the final release of task.io_context. Also protects ->cpuset and - * ->cgroup.subsys[]. + * ->cgroup.subsys[]. And ->vfork_done. * * Nests both inside and outside of read_lock(&tasklist_lock). * It must not be nested with write_lock_irq(&tasklist_lock), -- cgit v1.2.3 From 57b59c4a1400fa6c34764eab2e35a8762dc05a09 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 5 Mar 2012 14:59:13 -0800 Subject: coredump_wait: don't call complete_vfork_done() Now that CLONE_VFORK is killable, coredump_wait() no longer needs complete_vfork_done(). zap_threads() should find and kill all tasks with the same ->mm, this includes our parent if ->vfork_done is set. mm_release() becomes the only caller, unexport complete_vfork_done(). Signed-off-by: Oleg Nesterov Acked-by: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sched.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include') diff --git a/include/linux/sched.h b/include/linux/sched.h index b6467711f12e..11fcafaf4ae4 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2291,7 +2291,6 @@ extern int do_execve(const char *, const char __user * const __user *, const char __user * const __user *, struct pt_regs *); extern long do_fork(unsigned long, unsigned long, struct pt_regs *, unsigned long, int __user *, int __user *); -extern void complete_vfork_done(struct task_struct *tsk); struct task_struct *fork_idle(int); extern void set_task_comm(struct task_struct *tsk, char *from); -- cgit v1.2.3 From 6e27f63edbd7ab893258e16500171dd1270a1369 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 5 Mar 2012 14:59:14 -0800 Subject: vfork: kill PF_STARTING Previously it was (ab)used by utrace. Then it was wrongly used by the scheduler code. Currently it is not used, kill it before it finds the new erroneous user. Signed-off-by: Oleg Nesterov Acked-by: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sched.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include') diff --git a/include/linux/sched.h b/include/linux/sched.h index 11fcafaf4ae4..0657368bd78f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1777,7 +1777,6 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t * /* * Per process flags */ -#define PF_STARTING 0x00000002 /* being created */ #define PF_EXITING 0x00000004 /* getting shut down */ #define PF_EXITPIDONE 0x00000008 /* pi exit done on shut down */ #define PF_VCPU 0x00000010 /* I'm a virtual CPU */ -- cgit v1.2.3 From 7512102cf64d36e3c7444480273623c7aab3563f Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 5 Mar 2012 14:59:18 -0800 Subject: memcg: fix GPF when cgroup removal races with last exit When moving tasks from old memcg (with move_charge_at_immigrate on new memcg), followed by removal of old memcg, hit General Protection Fault in mem_cgroup_lru_del_list() (called from release_pages called from free_pages_and_swap_cache from tlb_flush_mmu from tlb_finish_mmu from exit_mmap from mmput from exit_mm from do_exit). Somewhat reproducible, takes a few hours: the old struct mem_cgroup has been freed and poisoned by SLAB_DEBUG, but mem_cgroup_lru_del_list() is still trying to update its stats, and take page off lru before freeing. A task, or a charge, or a page on lru: each secures a memcg against removal. In this case, the last task has been moved out of the old memcg, and it is exiting: anonymous pages are uncharged one by one from the memcg, as they are zapped from its pagetables, so the charge gets down to 0; but the pages themselves are queued in an mmu_gather for freeing. Most of those pages will be on lru (and force_empty is careful to lru_add_drain_all, to add pages from pagevec to lru first), but not necessarily all: perhaps some have been isolated for page reclaim, perhaps some isolated for other reasons. So, force_empty may find no task, no charge and no page on lru, and let the removal proceed. There would still be no problem if these pages were immediately freed; but typically (and the put_page_testzero protocol demands it) they have to be added back to lru before they are found freeable, then removed from lru and freed. We don't see the issue when adding, because the mem_cgroup_iter() loops keep their own reference to the memcg being scanned; but when it comes to mem_cgroup_lru_del_list(). I believe this was not an issue in v3.2: there, PageCgroupAcctLRU and PageCgroupUsed flags were used (like a trick with mirrors) to deflect view of pc->mem_cgroup to the stable root_mem_cgroup when neither set. 38c5d72f3ebe ("memcg: simplify LRU handling by new rule") mercifully removed those convolutions, but left this General Protection Fault. But it's surprisingly easy to restore the old behaviour: just check PageCgroupUsed in mem_cgroup_lru_add_list() (which decides on which lruvec to add), and reset pc to root_mem_cgroup if page is uncharged. A risky change? just going back to how it worked before; testing, and an audit of uses of pc->mem_cgroup, show no problem. And there's a nice bonus: with mem_cgroup_lru_add_list() itself making sure that an uncharged page goes to root lru, mem_cgroup_reset_owner() no longer has any purpose, and we can safely revert 4e5f01c2b9b9 ("memcg: clear pc->mem_cgroup if necessary"). Calling update_page_reclaim_stat() after add_page_to_lru_list() in swap.c is not strictly necessary: the lru_lock there, with RCU before memcg structures are freed, makes mem_cgroup_get_reclaim_stat_from_page safe without that; but it seems cleaner to rely on one dependency less. Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Johannes Weiner Cc: Konstantin Khlebnikov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/memcontrol.h | 5 ----- 1 file changed, 5 deletions(-) (limited to 'include') diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 4d34356fe644..b80de520670b 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -129,7 +129,6 @@ extern void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, extern void mem_cgroup_replace_page_cache(struct page *oldpage, struct page *newpage); -extern void mem_cgroup_reset_owner(struct page *page); #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP extern int do_swap_account; #endif @@ -392,10 +391,6 @@ static inline void mem_cgroup_replace_page_cache(struct page *oldpage, struct page *newpage) { } - -static inline void mem_cgroup_reset_owner(struct page *page) -{ -} #endif /* CONFIG_CGROUP_MEM_CONT */ #if !defined(CONFIG_CGROUP_MEM_RES_CTLR) || !defined(CONFIG_DEBUG_VM) -- cgit v1.2.3