From 92ee383f6daab4da5471b86f6fdaba775e6928f6 Mon Sep 17 00:00:00 2001 From: Shakeel Butt Date: Thu, 14 Jun 2018 15:26:27 -0700 Subject: mm: fix race between kmem_cache destroy, create and deactivate The memcg kmem cache creation and deactivation (SLUB only) is asynchronous. If a root kmem cache is destroyed whose memcg cache is in the process of creation or deactivation, the kernel may crash. Example of one such crash: general protection fault: 0000 [#1] SMP PTI CPU: 1 PID: 1721 Comm: kworker/14:1 Not tainted 4.17.0-smp ... Workqueue: memcg_kmem_cache kmemcg_deactivate_workfn RIP: 0010:has_cpu_slab ... Call Trace: ? on_each_cpu_cond __kmem_cache_shrink kmemcg_cache_deact_after_rcu kmemcg_deactivate_workfn process_one_work worker_thread kthread ret_from_fork+0x35/0x40 To fix this race, on root kmem cache destruction, mark the cache as dying and flush the workqueue used for memcg kmem cache creation and deactivation. SLUB's memcg kmem cache deactivation also includes RCU callback and thus make sure all previous registered RCU callbacks have completed as well. [shakeelb@google.com: handle the RCU callbacks for SLUB deactivation] Link: http://lkml.kernel.org/r/20180611192951.195727-1-shakeelb@google.com [shakeelb@google.com: add more documentation, rename fields for readability] Link: http://lkml.kernel.org/r/20180522201336.196994-1-shakeelb@google.com [akpm@linux-foundation.org: fix build, per Shakeel] [shakeelb@google.com: v3. Instead of refcount, flush the workqueue] Link: http://lkml.kernel.org/r/20180530001204.183758-1-shakeelb@google.com Link: http://lkml.kernel.org/r/20180521174116.171846-1-shakeelb@google.com Signed-off-by: Shakeel Butt Acked-by: Vladimir Davydov Cc: Michal Hocko Cc: Greg Thelen Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Johannes Weiner Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/slab.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux') diff --git a/include/linux/slab.h b/include/linux/slab.h index 4d759e1ddc33..14e3fe4bd6a1 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -600,6 +600,7 @@ struct memcg_cache_params { struct memcg_cache_array __rcu *memcg_caches; struct list_head __root_caches_node; struct list_head children; + bool dying; }; struct { struct mem_cgroup *memcg; -- cgit v1.2.3 From 0ed557aa813922f6f32adec69e266532091c895b Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Thu, 14 Jun 2018 15:27:41 -0700 Subject: sched/core / kcov: avoid kcov_area during task switch During a context switch, we first switch_mm() to the next task's mm, then switch_to() that new task. This means that vmalloc'd regions which had previously been faulted in can transiently disappear in the context of the prev task. Functions instrumented by KCOV may try to access a vmalloc'd kcov_area during this window, and as the fault handling code is instrumented, this results in a recursive fault. We must avoid accessing any kcov_area during this window. We can do so with a new flag in kcov_mode, set prior to switching the mm, and cleared once the new task is live. Since task_struct::kcov_mode isn't always a specific enum kcov_mode value, this is made an unsigned int. The manipulation is hidden behind kcov_{prepare,finish}_switch() helpers, which are empty for !CONFIG_KCOV kernels. The code uses macros because I can't use static inline functions without a circular include dependency between and , since the definition of task_struct uses things defined in Link: http://lkml.kernel.org/r/20180504135535.53744-4-mark.rutland@arm.com Signed-off-by: Mark Rutland Acked-by: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kcov.h | 14 ++++++++++++++ include/linux/sched.h | 2 +- 2 files changed, 15 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/kcov.h b/include/linux/kcov.h index 3ecf6f5e3a5f..b76a1807028d 100644 --- a/include/linux/kcov.h +++ b/include/linux/kcov.h @@ -22,13 +22,27 @@ enum kcov_mode { KCOV_MODE_TRACE_CMP = 3, }; +#define KCOV_IN_CTXSW (1 << 30) + void kcov_task_init(struct task_struct *t); void kcov_task_exit(struct task_struct *t); +#define kcov_prepare_switch(t) \ +do { \ + (t)->kcov_mode |= KCOV_IN_CTXSW; \ +} while (0) + +#define kcov_finish_switch(t) \ +do { \ + (t)->kcov_mode &= ~KCOV_IN_CTXSW; \ +} while (0) + #else static inline void kcov_task_init(struct task_struct *t) {} static inline void kcov_task_exit(struct task_struct *t) {} +static inline void kcov_prepare_switch(struct task_struct *t) {} +static inline void kcov_finish_switch(struct task_struct *t) {} #endif /* CONFIG_KCOV */ #endif /* _LINUX_KCOV_H */ diff --git a/include/linux/sched.h b/include/linux/sched.h index cfb7da88c217..87bf02d93a27 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1130,7 +1130,7 @@ struct task_struct { #ifdef CONFIG_KCOV /* Coverage collection mode enabled for this task (0 if disabled): */ - enum kcov_mode kcov_mode; + unsigned int kcov_mode; /* Size of the kcov_area: */ unsigned int kcov_size; -- cgit v1.2.3 From fe6bdfc8e1e131720abbe77a2eb990c94c9024cb Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Thu, 14 Jun 2018 15:28:05 -0700 Subject: mm: fix oom_kill event handling Commit e27be240df53 ("mm: memcg: make sure memory.events is uptodate when waking pollers") converted most of memcg event counters to per-memcg atomics, which made them less confusing for a user. The "oom_kill" counter remained untouched, so now it behaves differently than other counters (including "oom"). This adds nothing but confusion. Let's fix this by adding the MEMCG_OOM_KILL event, and follow the MEMCG_OOM approach. This also removes a hack from count_memcg_event_mm(), introduced earlier specially for the OOM_KILL counter. [akpm@linux-foundation.org: fix for droppage of memcg-replace-mm-owner-with-mm-memcg.patch] Link: http://lkml.kernel.org/r/20180508124637.29984-1-guro@fb.com Signed-off-by: Roman Gushchin Acked-by: Konstantin Khlebnikov Acked-by: Johannes Weiner Acked-by: Michal Hocko Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/memcontrol.h | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-) (limited to 'include/linux') diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 4f52ec755725..6c6fb116e925 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -53,6 +53,7 @@ enum memcg_memory_event { MEMCG_HIGH, MEMCG_MAX, MEMCG_OOM, + MEMCG_OOM_KILL, MEMCG_SWAP_MAX, MEMCG_SWAP_FAIL, MEMCG_NR_MEMORY_EVENTS, @@ -720,11 +721,8 @@ static inline void count_memcg_event_mm(struct mm_struct *mm, rcu_read_lock(); memcg = mem_cgroup_from_task(rcu_dereference(mm->owner)); - if (likely(memcg)) { + if (likely(memcg)) count_memcg_events(memcg, idx, 1); - if (idx == OOM_KILL) - cgroup_file_notify(&memcg->events_file); - } rcu_read_unlock(); } @@ -735,6 +733,21 @@ static inline void memcg_memory_event(struct mem_cgroup *memcg, cgroup_file_notify(&memcg->events_file); } +static inline void memcg_memory_event_mm(struct mm_struct *mm, + enum memcg_memory_event event) +{ + struct mem_cgroup *memcg; + + if (mem_cgroup_disabled()) + return; + + rcu_read_lock(); + memcg = mem_cgroup_from_task(rcu_dereference(mm->owner)); + if (likely(memcg)) + memcg_memory_event(memcg, event); + rcu_read_unlock(); +} + #ifdef CONFIG_TRANSPARENT_HUGEPAGE void mem_cgroup_split_huge_fixup(struct page *head); #endif @@ -756,6 +769,11 @@ static inline void memcg_memory_event(struct mem_cgroup *memcg, { } +static inline void memcg_memory_event_mm(struct mm_struct *mm, + enum memcg_memory_event event) +{ +} + static inline enum mem_cgroup_protection mem_cgroup_protected( struct mem_cgroup *root, struct mem_cgroup *memcg) { -- cgit v1.2.3