From 56dd9470d7c8734f055da2a6bac553caf4a468eb Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sun, 24 Feb 2013 00:23:25 +0100 Subject: context_tracking: Move exception handling to generic code Exceptions handling on context tracking should share common treatment: on entry we exit user mode if the exception triggered in that context. Then on exception exit we return to that previous context. Generalize this to avoid duplication across archs. Signed-off-by: Frederic Weisbecker Cc: Li Zhong Cc: Kevin Hilman Cc: Mats Liljegren Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Steven Rostedt Cc: Namhyung Kim Cc: Andrew Morton Cc: Thomas Gleixner Cc: Paul E. McKenney --- include/linux/context_tracking.h | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index b28d161c1091..5a69273e93e6 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -1,10 +1,11 @@ #ifndef _LINUX_CONTEXT_TRACKING_H #define _LINUX_CONTEXT_TRACKING_H -#ifdef CONFIG_CONTEXT_TRACKING #include #include +#include +#ifdef CONFIG_CONTEXT_TRACKING struct context_tracking { /* * When active is false, probes are unset in order @@ -33,12 +34,26 @@ static inline bool context_tracking_active(void) extern void user_enter(void); extern void user_exit(void); + +static inline void exception_enter(struct pt_regs *regs) +{ + user_exit(); +} + +static inline void exception_exit(struct pt_regs *regs) +{ + if (user_mode(regs)) + user_enter(); +} + extern void context_tracking_task_switch(struct task_struct *prev, struct task_struct *next); #else static inline bool context_tracking_in_user(void) { return false; } static inline void user_enter(void) { } static inline void user_exit(void) { } +static inline void exception_enter(struct pt_regs *regs) { } +static inline void exception_exit(struct pt_regs *regs) { } static inline void context_tracking_task_switch(struct task_struct *prev, struct task_struct *next) { } #endif /* !CONFIG_CONTEXT_TRACKING */ -- cgit v1.2.3 From 6c1e0256fad84a843d915414e4b5973b7443d48d Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sun, 24 Feb 2013 01:19:14 +0100 Subject: context_tracking: Restore correct previous context state on exception exit On exception exit, we restore the previous context tracking state based on the regs of the interrupted frame. Iff that frame is in user mode as stated by user_mode() helper, we restore the context tracking user mode. However there is a tiny chunck of low level arch code after we pass through user_enter() and until the CPU eventually resumes userspace. If an exception happens in this tiny area, exception_enter() correctly exits the context tracking user mode but exception_exit() won't restore it because of the value returned by user_mode(regs). As a result we may return to userspace with the wrong context tracking state. To fix this, change exception_enter() to return the context tracking state prior to its call and pass this saved state to exception_exit(). This restores the real context tracking state of the interrupted frame. (May be this patch was suggested to me, I don't recall exactly. If so, sorry for the missing credit). Signed-off-by: Frederic Weisbecker Cc: Li Zhong Cc: Kevin Hilman Cc: Mats Liljegren Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Steven Rostedt Cc: Namhyung Kim Cc: Andrew Morton Cc: Thomas Gleixner Cc: Paul E. McKenney --- include/linux/context_tracking.h | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) (limited to 'include/linux') diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index 5a69273e93e6..365f4a61bf04 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -5,7 +5,6 @@ #include #include -#ifdef CONFIG_CONTEXT_TRACKING struct context_tracking { /* * When active is false, probes are unset in order @@ -14,12 +13,13 @@ struct context_tracking { * may be further optimized using static keys. */ bool active; - enum { + enum ctx_state { IN_KERNEL = 0, IN_USER, } state; }; +#ifdef CONFIG_CONTEXT_TRACKING DECLARE_PER_CPU(struct context_tracking, context_tracking); static inline bool context_tracking_in_user(void) @@ -35,14 +35,19 @@ static inline bool context_tracking_active(void) extern void user_enter(void); extern void user_exit(void); -static inline void exception_enter(struct pt_regs *regs) +static inline enum ctx_state exception_enter(void) { + enum ctx_state prev_ctx; + + prev_ctx = this_cpu_read(context_tracking.state); user_exit(); + + return prev_ctx; } -static inline void exception_exit(struct pt_regs *regs) +static inline void exception_exit(enum ctx_state prev_ctx) { - if (user_mode(regs)) + if (prev_ctx == IN_USER) user_enter(); } @@ -52,8 +57,8 @@ extern void context_tracking_task_switch(struct task_struct *prev, static inline bool context_tracking_in_user(void) { return false; } static inline void user_enter(void) { } static inline void user_exit(void) { } -static inline void exception_enter(struct pt_regs *regs) { } -static inline void exception_exit(struct pt_regs *regs) { } +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 */ -- cgit v1.2.3 From 9fbc42eac1f6917081dc3b39922b2f1c57fdff28 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 25 Feb 2013 17:25:39 +0100 Subject: cputime: Dynamically scale cputime for full dynticks accounting The full dynticks cputime accounting is able to account either using the tick or the context tracking subsystem. This way the housekeeping CPU can keep the low overhead tick based solution. This latter mode has a low jiffies resolution granularity and need to be scaled against CFS precise runtime accounting to improve its result. We are doing this for CONFIG_TICK_CPU_ACCOUNTING, now we also need to expand it to full dynticks accounting dynamic off-case as well. Signed-off-by: Frederic Weisbecker Cc: Li Zhong Cc: Kevin Hilman Cc: Mats Liljegren Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Steven Rostedt Cc: Namhyung Kim Cc: Andrew Morton Cc: Thomas Gleixner Cc: Paul E. McKenney --- include/linux/sched.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/sched.h b/include/linux/sched.h index d35d2b6ddbfb..8d1b6034d80b 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -570,7 +570,7 @@ struct signal_struct { cputime_t utime, stime, cutime, cstime; cputime_t gtime; cputime_t cgtime; -#ifndef CONFIG_VIRT_CPU_ACCOUNTING +#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE struct cputime prev_cputime; #endif unsigned long nvcsw, nivcsw, cnvcsw, cnivcsw; @@ -1327,7 +1327,7 @@ struct task_struct { cputime_t utime, stime, utimescaled, stimescaled; cputime_t gtime; -#ifndef CONFIG_VIRT_CPU_ACCOUNTING +#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE struct cputime prev_cputime; #endif #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN -- cgit v1.2.3