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Message-ID: <521AEA44.70608@hitachi.com>
Date: Mon, 26 Aug 2013 14:40:20 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Tom Zanussi <tom.zanussi@...ux.intel.com>
Cc: rostedt@...dmis.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 01/10] tracing: Add support for SOFT_DISABLE to syscall
events
(2013/08/23 8:27), Tom Zanussi wrote:
> The original SOFT_DISABLE patches didn't add support for soft disable
> of syscall events; this adds it and paves the way for future patches
> allowing triggers to be added to syscall events, since triggers are
> built on top of SOFT_DISABLE.
>
> Add an array of ftrace_event_file pointers indexed by syscall number
> to the trace array and remove the existing enabled bitmaps, which as a
> result are now redundant. The ftrace_event_file structs in turn
> contain the soft disable flags we need for per-syscall soft disable
> accounting; later patches add additional 'trigger' flags and
> per-syscall triggers and filters.
>
This looks good for me.
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
> ---
> kernel/trace/trace.h | 4 ++--
> kernel/trace/trace_syscalls.c | 36 ++++++++++++++++++++++++++++++------
> 2 files changed, 32 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index fe39acd..b1227b9 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -192,8 +192,8 @@ struct trace_array {
> #ifdef CONFIG_FTRACE_SYSCALLS
> int sys_refcount_enter;
> int sys_refcount_exit;
> - DECLARE_BITMAP(enabled_enter_syscalls, NR_syscalls);
> - DECLARE_BITMAP(enabled_exit_syscalls, NR_syscalls);
> + struct ftrace_event_file *enter_syscall_files[NR_syscalls];
> + struct ftrace_event_file *exit_syscall_files[NR_syscalls];
> #endif
> int stop_count;
> int clock_id;
> diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
> index 559329d..230cdb6 100644
> --- a/kernel/trace/trace_syscalls.c
> +++ b/kernel/trace/trace_syscalls.c
> @@ -302,6 +302,7 @@ static int __init syscall_exit_define_fields(struct ftrace_event_call *call)
> static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
> {
> struct trace_array *tr = data;
> + struct ftrace_event_file *ftrace_file;
> struct syscall_trace_enter *entry;
> struct syscall_metadata *sys_data;
> struct ring_buffer_event *event;
> @@ -314,7 +315,13 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
> syscall_nr = trace_get_syscall_nr(current, regs);
> if (syscall_nr < 0)
> return;
> - if (!test_bit(syscall_nr, tr->enabled_enter_syscalls))
> +
> + /* Here we're inside the tp handler's rcu_read_lock (__DO_TRACE()) */
> + ftrace_file = rcu_dereference_raw(tr->enter_syscall_files[syscall_nr]);
> + if (!ftrace_file)
> + return;
> +
> + if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &ftrace_file->flags))
> return;
>
> sys_data = syscall_nr_to_meta(syscall_nr);
> @@ -345,6 +352,7 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
> static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
> {
> struct trace_array *tr = data;
> + struct ftrace_event_file *ftrace_file;
> struct syscall_trace_exit *entry;
> struct syscall_metadata *sys_data;
> struct ring_buffer_event *event;
> @@ -356,7 +364,13 @@ static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
> syscall_nr = trace_get_syscall_nr(current, regs);
> if (syscall_nr < 0)
> return;
> - if (!test_bit(syscall_nr, tr->enabled_exit_syscalls))
> +
> + /* Here we're inside the tp handler's rcu_read_lock (__DO_TRACE()) */
> + ftrace_file = rcu_dereference_raw(tr->exit_syscall_files[syscall_nr]);
> + if (!ftrace_file)
> + return;
> +
> + if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &ftrace_file->flags))
> return;
>
> sys_data = syscall_nr_to_meta(syscall_nr);
> @@ -397,7 +411,7 @@ static int reg_event_syscall_enter(struct ftrace_event_file *file,
> if (!tr->sys_refcount_enter)
> ret = register_trace_sys_enter(ftrace_syscall_enter, tr);
> if (!ret) {
> - set_bit(num, tr->enabled_enter_syscalls);
> + rcu_assign_pointer(tr->enter_syscall_files[num], file);
> tr->sys_refcount_enter++;
> }
> mutex_unlock(&syscall_trace_lock);
> @@ -415,9 +429,14 @@ static void unreg_event_syscall_enter(struct ftrace_event_file *file,
> return;
> mutex_lock(&syscall_trace_lock);
> tr->sys_refcount_enter--;
> - clear_bit(num, tr->enabled_enter_syscalls);
> + rcu_assign_pointer(tr->enter_syscall_files[num], NULL);
> if (!tr->sys_refcount_enter)
> unregister_trace_sys_enter(ftrace_syscall_enter, tr);
> + /*
> + * Callers expect the event to be completely disabled on
> + * return, so wait for current handlers to finish.
> + */
> + synchronize_sched();
> mutex_unlock(&syscall_trace_lock);
> }
>
> @@ -435,7 +454,7 @@ static int reg_event_syscall_exit(struct ftrace_event_file *file,
> if (!tr->sys_refcount_exit)
> ret = register_trace_sys_exit(ftrace_syscall_exit, tr);
> if (!ret) {
> - set_bit(num, tr->enabled_exit_syscalls);
> + rcu_assign_pointer(tr->exit_syscall_files[num], file);
> tr->sys_refcount_exit++;
> }
> mutex_unlock(&syscall_trace_lock);
> @@ -453,9 +472,14 @@ static void unreg_event_syscall_exit(struct ftrace_event_file *file,
> return;
> mutex_lock(&syscall_trace_lock);
> tr->sys_refcount_exit--;
> - clear_bit(num, tr->enabled_exit_syscalls);
> + rcu_assign_pointer(tr->exit_syscall_files[num], NULL);
> if (!tr->sys_refcount_exit)
> unregister_trace_sys_exit(ftrace_syscall_exit, tr);
> + /*
> + * Callers expect the event to be completely disabled on
> + * return, so wait for current handlers to finish.
> + */
> + synchronize_sched();
> mutex_unlock(&syscall_trace_lock);
> }
>
>
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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