From 97419875865859fd2403e66266c02ce028e2f5ab Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Mon, 24 Aug 2009 14:43:13 -0700 Subject: tracing: Move tracepoint callbacks from declaration to definition It's not strictly correct for the tracepoint reg/unreg callbacks to occur when a client is hooking up, because the actual tracepoint may not be present yet. This happens to be fine for syscall, since that's in the core kernel, but it would cause problems for tracepoints defined in a module that hasn't been loaded yet. It also means the reg/unreg has to be EXPORTed for any modules to use the tracepoint (as in SystemTap). This patch removes DECLARE_TRACE_WITH_CALLBACK, and instead introduces DEFINE_TRACE_FN which stores the callbacks in struct tracepoint. The callbacks are used now when the active state of the tracepoint changes in set_tracepoint & disable_tracepoint. This also introduces TRACE_EVENT_FN, so ftrace events can also provide registration callbacks if needed. Signed-off-by: Josh Stone Cc: Jason Baron Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Li Zefan Cc: Steven Rostedt Cc: Peter Zijlstra Cc: Mathieu Desnoyers Cc: Jiaying Zhang Cc: Martin Bligh Cc: Lai Jiangshan Cc: Paul Mundt Cc: Martin Schwidefsky Cc: Heiko Carstens LKML-Reference: <1251150194-1713-4-git-send-email-jistone@redhat.com> Signed-off-by: Frederic Weisbecker --- kernel/tracepoint.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) (limited to 'kernel/tracepoint.c') diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 9e0a36f0e2a9..1a6a453b7efb 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -243,6 +243,11 @@ static void set_tracepoint(struct tracepoint_entry **entry, { WARN_ON(strcmp((*entry)->name, elem->name) != 0); + if (elem->regfunc && !elem->state && active) + elem->regfunc(); + else if (elem->unregfunc && elem->state && !active) + elem->unregfunc(); + /* * rcu_assign_pointer has a smp_wmb() which makes sure that the new * probe callbacks array is consistent before setting a pointer to it. @@ -262,6 +267,9 @@ static void set_tracepoint(struct tracepoint_entry **entry, */ static void disable_tracepoint(struct tracepoint *elem) { + if (elem->unregfunc && elem->state) + elem->unregfunc(); + elem->state = 0; rcu_assign_pointer(elem->funcs, NULL); } @@ -578,7 +586,7 @@ __initcall(init_tracepoints); #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS -static DEFINE_MUTEX(regfunc_mutex); +/* NB: reg/unreg are called while guarded with the tracepoints_mutex */ static int sys_tracepoint_refcount; void syscall_regfunc(void) @@ -586,7 +594,6 @@ void syscall_regfunc(void) unsigned long flags; struct task_struct *g, *t; - mutex_lock(®func_mutex); if (!sys_tracepoint_refcount) { read_lock_irqsave(&tasklist_lock, flags); do_each_thread(g, t) { @@ -595,7 +602,6 @@ void syscall_regfunc(void) read_unlock_irqrestore(&tasklist_lock, flags); } sys_tracepoint_refcount++; - mutex_unlock(®func_mutex); } void syscall_unregfunc(void) @@ -603,7 +609,6 @@ void syscall_unregfunc(void) unsigned long flags; struct task_struct *g, *t; - mutex_lock(®func_mutex); sys_tracepoint_refcount--; if (!sys_tracepoint_refcount) { read_lock_irqsave(&tasklist_lock, flags); @@ -612,6 +617,5 @@ void syscall_unregfunc(void) } while_each_thread(g, t); read_unlock_irqrestore(&tasklist_lock, flags); } - mutex_unlock(®func_mutex); } #endif -- cgit