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SubjectRe: [PATCH] tracing: Move tracepoint callbacks into DEFINE
On 08/19/2009 09:13 AM, Jason Baron wrote:
> On Tue, Aug 18, 2009 at 12:23:47AM -0700, Josh Stone wrote:
>> --- 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);
>> }
>> @@ -581,15 +589,13 @@ __initcall(init_tracepoints);
>>
>> #ifdef CONFIG_FTRACE_SYSCALLS
>>
>> -static DEFINE_MUTEX(regfunc_mutex);
>> -static int sys_tracepoint_refcount;
>> +static int sys_tracepoint_refcount; /* guarded by tracepoints_mutex */
>>
>> void syscall_regfunc(void)
>> {
>> unsigned long flags;
>> struct task_struct *g, *t;
>>
>> - mutex_lock(&regfunc_mutex);
>> if (!sys_tracepoint_refcount) {
>> read_lock_irqsave(&tasklist_lock, flags);
>> do_each_thread(g, t) {
>> @@ -598,7 +604,6 @@ void syscall_regfunc(void)
>> read_unlock_irqrestore(&tasklist_lock, flags);
>> }
>> sys_tracepoint_refcount++;
>> - mutex_unlock(&regfunc_mutex);
>> }
>>
>> void syscall_unregfunc(void)
>> @@ -606,7 +611,6 @@ void syscall_unregfunc(void)
>> unsigned long flags;
>> struct task_struct *g, *t;
>>
>> - mutex_lock(&regfunc_mutex);
>> sys_tracepoint_refcount--;
>> if (!sys_tracepoint_refcount) {
>> read_lock_irqsave(&tasklist_lock, flags);
>> @@ -615,6 +619,5 @@ void syscall_unregfunc(void)
>> } while_each_thread(g, t);
>> read_unlock_irqrestore(&tasklist_lock, flags);
>> }
>> - mutex_unlock(&regfunc_mutex);
>> }
>> #endif
>
> if we disable, CONFIG_FTRACE_SYSCALLS, then we get undefined references
> to syscall_regfunc, and syscall_unregfunc. So, i think we just need to
> remove the 'CONFIG_FTRACE_SYSCALLS' ifdef here.

This CONFIG check was added by commit 60d970c2 to deal with missing
TIF_SYSCALL_FTRACE. Perhaps the functions should just have their bodies
#ifdef'ed?

Josh


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