linux-kernel - Re: [PATCH v3 2/4] tracing: Make syscall

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Date:	Sun, 23 Aug 2009 23:14:24 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Josh Stone <jistone@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Jason Baron <jbaron@...hat.com>,
	Ingo Molnar <mingo@...e.hu>, Li Zefan <lizf@...fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Jiaying Zhang <jiayingz@...gle.com>,
	Martin Bligh <mbligh@...gle.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [PATCH v3 2/4] tracing: Make syscall_(un)regfunc arch-specific

On Fri, Aug 21, 2009 at 09:58:43PM -0700, Josh Stone wrote:
> The bodies of syscall_regfunc and syscall_unregfunc need the
> arch-specific flag TIF_SYSCALL_TRACEPOINT, which only exists
> on x86 and s390, so they should live in arch-specific files.


Sh also does, but currently in a seperate development branch.
(Adding Paul Mundt in Cc to prevent from further linux-next breakage).


 
> +
> +#ifdef CONFIG_TRACEPOINTS
> +
> +static DEFINE_MUTEX(regfunc_mutex);
> +static int sys_tracepoint_refcount;
> +
> +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) {
> +			set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
> +		} while_each_thread(g, t);
> +		read_unlock_irqrestore(&tasklist_lock, flags);
> +	}
> +	sys_tracepoint_refcount++;
> +	mutex_unlock(&regfunc_mutex);
> +}
> +
> +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);
> +		do_each_thread(g, t) {
> +			clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
> +		} while_each_thread(g, t);
> +		read_unlock_irqrestore(&tasklist_lock, flags);
> +	}
> +	mutex_unlock(&regfunc_mutex);
> +}
> +#endif
> diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
> index a909afe..c2adbed 100644
> --- a/arch/x86/kernel/ptrace.c
> +++ b/arch/x86/kernel/ptrace.c
> @@ -1549,3 +1549,43 @@ asmregparm void syscall_trace_leave(struct pt_regs *regs)
>  	    tracehook_consider_fatal_signal(current, SIGTRAP))
>  		send_sigtrap(current, regs, 0, TRAP_BRKPT);
>  }
> +
> +#ifdef CONFIG_TRACEPOINTS
> +
> +static DEFINE_MUTEX(regfunc_mutex);
> +static int sys_tracepoint_refcount;
> +
> +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) {
> +			set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
> +		} while_each_thread(g, t);
> +		read_unlock_irqrestore(&tasklist_lock, flags);
> +	}
> +	sys_tracepoint_refcount++;
> +	mutex_unlock(&regfunc_mutex);
> +}
> +
> +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);
> +		do_each_thread(g, t) {
> +			clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
> +		} while_each_thread(g, t);
> +		read_unlock_irqrestore(&tasklist_lock, flags);
> +	}
> +	mutex_unlock(&regfunc_mutex);
> +}
> +#endif



I really don't like that.
See how the s390 and x86 version of the above code are completely
identical?

Please put this in kernel/ptrace.c

Thanks.

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