From aed5ed47724f6a7453fa62e3c90f3cee93edbfe3 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 6 May 2015 18:04:23 +0200 Subject: context_tracking: Protect against recursion Context tracking recursion can happen when an exception triggers in the middle of a call to a context tracking probe. This special case can be caused by vmalloc faults. If an access to a memory area allocated by vmalloc happens in the middle of context_tracking_enter(), we may run into an endless fault loop because the exception in turn calls context_tracking_enter() which faults on the same vmalloc'ed memory, triggering an exception again, etc... Some rare crashes have been reported so lets protect against this with a recursion counter. Reported-by: Dave Jones Signed-off-by: Frederic Weisbecker Reviewed-by: Rik van Riel Acked-by: Peter Zijlstra (Intel) Cc: Borislav Petkov Cc: Chris Metcalf Cc: H. Peter Anvin Cc: Martin Schwidefsky Cc: Mike Galbraith Cc: Oleg Nesterov Cc: Paul E. McKenney Cc: Rafael J . Wysocki Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1430928266-24888-2-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar --- include/linux/context_tracking_state.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h index 6b7b96a32b75..678ecdf90cf6 100644 --- a/include/linux/context_tracking_state.h +++ b/include/linux/context_tracking_state.h @@ -12,6 +12,7 @@ struct context_tracking { * may be further optimized using static keys. */ bool active; + int recursion; enum ctx_state { CONTEXT_KERNEL = 0, CONTEXT_USER, -- cgit v1.2.3 From fafe870f31212a72f3c2d74e7b90e4ef39e83ee1 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 6 May 2015 18:04:24 +0200 Subject: context_tracking: Inherit TIF_NOHZ through forks instead of context switches TIF_NOHZ is used by context_tracking to force syscall slow-path on every task in order to track userspace roundtrips. As such, it must be set on all running tasks. It's currently explicitly inherited through context switches. There is no need to do it in this fast-path though. The flag could simply be set once for all on all tasks, whether they are running or not. Lets do this by setting the flag for the init task on early boot, and let it propagate through fork inheritance. While at it, mark context_tracking_cpu_set() as init code, we only need it at early boot time. Suggested-by: Oleg Nesterov Signed-off-by: Frederic Weisbecker Reviewed-by: Rik van Riel Cc: Borislav Petkov Cc: Chris Metcalf Cc: Dave Jones Cc: H. Peter Anvin Cc: Martin Schwidefsky Cc: Mike Galbraith Cc: Paul E . McKenney Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rafael J . Wysocki Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1430928266-24888-3-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar --- include/linux/context_tracking.h | 10 ---------- include/linux/sched.h | 3 +++ 2 files changed, 3 insertions(+), 10 deletions(-) (limited to 'include') diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index 2821838256b4..b96bd299966f 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -14,8 +14,6 @@ extern void context_tracking_enter(enum ctx_state state); extern void context_tracking_exit(enum ctx_state state); extern void context_tracking_user_enter(void); extern void context_tracking_user_exit(void); -extern void __context_tracking_task_switch(struct task_struct *prev, - struct task_struct *next); static inline void user_enter(void) { @@ -51,19 +49,11 @@ static inline void exception_exit(enum ctx_state prev_ctx) } } -static inline void context_tracking_task_switch(struct task_struct *prev, - struct task_struct *next) -{ - if (context_tracking_is_enabled()) - __context_tracking_task_switch(prev, next); -} #else static inline void user_enter(void) { } static inline void user_exit(void) { } static inline enum ctx_state exception_enter(void) { return 0; } static inline void exception_exit(enum ctx_state prev_ctx) { } -static inline void context_tracking_task_switch(struct task_struct *prev, - struct task_struct *next) { } #endif /* !CONFIG_CONTEXT_TRACKING */ diff --git a/include/linux/sched.h b/include/linux/sched.h index 26a2e6122734..185a750e4ed4 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2532,6 +2532,9 @@ static inline unsigned long wait_task_inactive(struct task_struct *p, } #endif +#define tasklist_empty() \ + list_empty(&init_task.tasks) + #define next_task(p) \ list_entry_rcu((p)->tasks.next, struct task_struct, tasks) -- cgit v1.2.3 From 83dedea8a07fb4bf91863764b15c1c4ec00330f9 Mon Sep 17 00:00:00 2001 From: Chris Metcalf Date: Wed, 6 May 2015 18:04:25 +0200 Subject: nohz: Add tick_nohz_full_add_cpus_to() API This API is useful to modify a cpumask indicating some special nohz-type functionality so that the nohz cores are automatically added to that set. Signed-off-by: Chris Metcalf Signed-off-by: Frederic Weisbecker Acked-by: Peter Zijlstra (Intel) Cc: Borislav Petkov Cc: Dave Jones Cc: H. Peter Anvin Cc: Martin Schwidefsky Cc: Mike Galbraith Cc: Oleg Nesterov Cc: Paul E. McKenney Cc: Rafael J. Wysocki Cc: Rik van Riel Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1429024675-18938-1-git-send-email-cmetcalf@ezchip.com Link: http://lkml.kernel.org/r/1430928266-24888-4-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar --- include/linux/tick.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include') diff --git a/include/linux/tick.h b/include/linux/tick.h index f8492da57ad3..4191b5623a28 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -134,6 +134,12 @@ static inline bool tick_nohz_full_cpu(int cpu) return cpumask_test_cpu(cpu, tick_nohz_full_mask); } +static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) +{ + if (tick_nohz_full_enabled()) + cpumask_or(mask, mask, tick_nohz_full_mask); +} + extern void __tick_nohz_full_check(void); extern void tick_nohz_full_kick(void); extern void tick_nohz_full_kick_cpu(int cpu); @@ -142,6 +148,7 @@ extern void __tick_nohz_task_switch(struct task_struct *tsk); #else static inline bool tick_nohz_full_enabled(void) { return false; } static inline bool tick_nohz_full_cpu(int cpu) { return false; } +static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { } static inline void __tick_nohz_full_check(void) { } static inline void tick_nohz_full_kick_cpu(int cpu) { } static inline void tick_nohz_full_kick(void) { } -- cgit v1.2.3