From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753542Ab1LULtQ (ORCPT ); Wed, 21 Dec 2011 06:49:16 -0500 Received: from mx1.redhat.com ([209.132.183.28]:13450 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752600Ab1LULtN (ORCPT ); Wed, 21 Dec 2011 06:49:13 -0500 From: Jiri Olsa To: rostedt@goodmis.org, fweisbec@gmail.com, mingo@redhat.com, paulus@samba.org, acme@ghostprotocols.net, a.p.zijlstra@chello.nl Cc: linux-kernel@vger.kernel.org, aarapov@redhat.com, Jiri Olsa Subject: [PATCH 3/8] ftrace: Add enable/disable ftrace_ops control interface Date: Wed, 21 Dec 2011 12:48:51 +0100 Message-Id: <1324468136-3997-4-git-send-email-jolsa@redhat.com> In-Reply-To: <1324468136-3997-1-git-send-email-jolsa@redhat.com> References: <1323105776-26961-1-git-send-email-jolsa@redhat.com> <1324468136-3997-1-git-send-email-jolsa@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Adding a way to temporarily enable/disable ftrace_ops. The change follows the same way as 'global' ftrace_ops are done. Introducing 2 global ftrace_ops - control_ops and ftrace_control_list which take over all ftrace_ops registered with FTRACE_OPS_FL_CONTROL flag. In addition new per cpu flag called 'disabled' is also added to ftrace_ops to provide the control information for each cpu. When ftrace_ops with FTRACE_OPS_FL_CONTROL is registered, it is set as disabled for all cpus. The ftrace_control_list contains all the registered 'control' ftrace_ops. The control_ops provides function which iterates ftrace_control_list and does the check for 'disabled' flag on current cpu. Adding 2 inline functions ftrace_function_enable/ftrace_function_disable, which enable/disable the ftrace_ops for given cpu. Signed-off-by: Jiri Olsa --- include/linux/ftrace.h | 42 +++++++++++++++++ kernel/trace/ftrace.c | 116 +++++++++++++++++++++++++++++++++++++++++++++--- kernel/trace/trace.h | 2 + 3 files changed, 153 insertions(+), 7 deletions(-) diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 523640f..67b8236 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -35,12 +35,14 @@ enum { FTRACE_OPS_FL_ENABLED = 1 << 0, FTRACE_OPS_FL_GLOBAL = 1 << 1, FTRACE_OPS_FL_DYNAMIC = 1 << 2, + FTRACE_OPS_FL_CONTROL = 1 << 3, }; struct ftrace_ops { ftrace_func_t func; struct ftrace_ops *next; unsigned long flags; + void __percpu *disabled; #ifdef CONFIG_DYNAMIC_FTRACE struct ftrace_hash *notrace_hash; struct ftrace_hash *filter_hash; @@ -97,6 +99,46 @@ int register_ftrace_function(struct ftrace_ops *ops); int unregister_ftrace_function(struct ftrace_ops *ops); void clear_ftrace_function(void); +/** + * ftrace_function_enable - enable controlled ftrace_ops on given cpu + * + * This function enables tracing on given cpu by decreasing + * the per cpu control variable. + * It must be called with preemption disabled and only on + * ftrace_ops registered with FTRACE_OPS_FL_CONTROL. + */ +static inline void ftrace_function_enable(struct ftrace_ops *ops, int cpu) +{ + atomic_t *disabled; + + if (WARN_ON_ONCE(!(ops->flags & FTRACE_OPS_FL_CONTROL)) || + !preempt_count()) + return; + + disabled = per_cpu_ptr(ops->disabled, cpu); + atomic_dec(disabled); +} + +/** + * ftrace_function_disable - enable controlled ftrace_ops on given cpu + * + * This function enables tracing on given cpu by decreasing + * the per cpu control variable. + * It must be called with preemption disabled and only on + * ftrace_ops registered with FTRACE_OPS_FL_CONTROL. + */ +static inline void ftrace_function_disable(struct ftrace_ops *ops, int cpu) +{ + atomic_t *disabled; + + if (WARN_ON_ONCE(!(ops->flags & FTRACE_OPS_FL_CONTROL)) || + !preempt_count()) + return; + + disabled = per_cpu_ptr(ops->disabled, cpu); + atomic_inc(disabled); +} + extern void ftrace_stub(unsigned long a0, unsigned long a1); #else /* !CONFIG_FUNCTION_TRACER */ diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 7eb702f..1b56013 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -60,6 +60,8 @@ #define FTRACE_HASH_DEFAULT_BITS 10 #define FTRACE_HASH_MAX_BITS 12 +#define FL_GLOBAL_CONTROL (FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_CONTROL) + /* ftrace_enabled is a method to turn ftrace on or off */ int ftrace_enabled __read_mostly; static int last_ftrace_enabled; @@ -87,12 +89,14 @@ static struct ftrace_ops ftrace_list_end __read_mostly = { }; static struct ftrace_ops *ftrace_global_list __read_mostly = &ftrace_list_end; +static struct ftrace_ops *ftrace_control_list __read_mostly = &ftrace_list_end; static struct ftrace_ops *ftrace_ops_list __read_mostly = &ftrace_list_end; ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub; static ftrace_func_t __ftrace_trace_function_delay __read_mostly = ftrace_stub; ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub; ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub; static struct ftrace_ops global_ops; +static struct ftrace_ops control_ops; static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip); @@ -166,6 +170,38 @@ static void ftrace_test_stop_func(unsigned long ip, unsigned long parent_ip) } #endif +static void control_ops_disable_all(struct ftrace_ops *ops) +{ + int cpu; + + for_each_possible_cpu(cpu) + atomic_set(per_cpu_ptr(ops->disabled, cpu), 1); +} + +static int control_ops_alloc(struct ftrace_ops *ops) +{ + atomic_t *disabled; + + disabled = alloc_percpu(atomic_t); + if (!disabled) + return -ENOMEM; + + ops->disabled = disabled; + control_ops_disable_all(ops); + return 0; +} + +static void control_ops_free(struct ftrace_ops *ops) +{ + free_percpu(ops->disabled); +} + +static int control_ops_is_disabled(struct ftrace_ops *ops) +{ + atomic_t *disabled = this_cpu_ptr(ops->disabled); + return atomic_read(disabled); +} + static void update_global_ops(void) { ftrace_func_t func; @@ -257,6 +293,26 @@ static int remove_ftrace_ops(struct ftrace_ops **list, struct ftrace_ops *ops) return 0; } +static void add_ftrace_list_ops(struct ftrace_ops **list, + struct ftrace_ops *main_ops, + struct ftrace_ops *ops) +{ + int first = *list == &ftrace_list_end; + add_ftrace_ops(list, ops); + if (first) + add_ftrace_ops(&ftrace_ops_list, main_ops); +} + +static int remove_ftrace_list_ops(struct ftrace_ops **list, + struct ftrace_ops *main_ops, + struct ftrace_ops *ops) +{ + int ret = remove_ftrace_ops(list, ops); + if (!ret && *list == &ftrace_list_end) + ret = remove_ftrace_ops(&ftrace_ops_list, main_ops); + return ret; +} + static int __register_ftrace_function(struct ftrace_ops *ops) { if (ftrace_disabled) @@ -268,15 +324,19 @@ static int __register_ftrace_function(struct ftrace_ops *ops) if (WARN_ON(ops->flags & FTRACE_OPS_FL_ENABLED)) return -EBUSY; + if ((ops->flags & FL_GLOBAL_CONTROL) == FL_GLOBAL_CONTROL) + return -EINVAL; + if (!core_kernel_data((unsigned long)ops)) ops->flags |= FTRACE_OPS_FL_DYNAMIC; if (ops->flags & FTRACE_OPS_FL_GLOBAL) { - int first = ftrace_global_list == &ftrace_list_end; - add_ftrace_ops(&ftrace_global_list, ops); + add_ftrace_list_ops(&ftrace_global_list, &global_ops, ops); ops->flags |= FTRACE_OPS_FL_ENABLED; - if (first) - add_ftrace_ops(&ftrace_ops_list, &global_ops); + } else if (ops->flags & FTRACE_OPS_FL_CONTROL) { + if (control_ops_alloc(ops)) + return -ENOMEM; + add_ftrace_list_ops(&ftrace_control_list, &control_ops, ops); } else add_ftrace_ops(&ftrace_ops_list, ops); @@ -300,11 +360,23 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops) return -EINVAL; if (ops->flags & FTRACE_OPS_FL_GLOBAL) { - ret = remove_ftrace_ops(&ftrace_global_list, ops); - if (!ret && ftrace_global_list == &ftrace_list_end) - ret = remove_ftrace_ops(&ftrace_ops_list, &global_ops); + ret = remove_ftrace_list_ops(&ftrace_global_list, + &global_ops, ops); if (!ret) ops->flags &= ~FTRACE_OPS_FL_ENABLED; + } else if (ops->flags & FTRACE_OPS_FL_CONTROL) { + ret = remove_ftrace_list_ops(&ftrace_control_list, + &control_ops, ops); + if (!ret) { + /* + * The ftrace_ops is now removed from the list, + * so there'll be no new users. We must ensure + * all current users are done before we free + * the control data. + */ + synchronize_sched(); + control_ops_free(ops); + } } else ret = remove_ftrace_ops(&ftrace_ops_list, ops); @@ -3566,6 +3638,36 @@ ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip) #endif /* CONFIG_DYNAMIC_FTRACE */ static void +ftrace_ops_control_func(unsigned long ip, unsigned long parent_ip) +{ + struct ftrace_ops *op; + + if (unlikely(trace_recursion_test(TRACE_CONTROL_BIT))) + return; + + /* + * Some of the ops may be dynamically allocated, + * they must be freed after a synchronize_sched(). + */ + preempt_disable_notrace(); + trace_recursion_set(TRACE_CONTROL_BIT); + op = rcu_dereference_raw(ftrace_control_list); + while (op != &ftrace_list_end) { + if (!control_ops_is_disabled(op) && + ftrace_ops_test(op, ip)) + op->func(ip, parent_ip); + + op = rcu_dereference_raw(op->next); + }; + trace_recursion_clear(TRACE_CONTROL_BIT); + preempt_enable_notrace(); +} + +static struct ftrace_ops control_ops = { + .func = ftrace_ops_control_func, +}; + +static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip) { struct ftrace_ops *op; diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 2c26574..41c54e3 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -288,6 +288,8 @@ struct tracer { /* for function tracing recursion */ #define TRACE_INTERNAL_BIT (1<<11) #define TRACE_GLOBAL_BIT (1<<12) +#define TRACE_CONTROL_BIT (1<<13) + /* * Abuse of the trace_recursion. * As we need a way to maintain state if we are tracing the function -- 1.7.1