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Date: Fri, 26 Feb 2016 10:57:13 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>
Cc: Taeung Song <treeze.taeung@...il.com>,
linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Lai Jiangshan <jiangshanlai@...il.com>
Subject: [RFC] Re: [PATCH v3 1/2] tracing/syscalls: Rename variable 'nr' to
'__syscall_nr'
Em Fri, Feb 26, 2016 at 10:14:06PM +0900, Taeung Song escreveu:
> There is a problem about duplicated variable name i.e.
>
> # cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_io_getevents/format
> name: sys_enter_io_getevents
> ID: 739
> format:
Steven, what do you think?
Should we break this ABI while disambiguating the 'nr' field, using
'__syscall_nr' in an attempt to use a name that is unlikely to be used
by a real syscall argument name?
If we stand by published ABIs, we should keep it written in stone and
state that the first 'nr' means '__syscall_nr' while keeping it as-is,
the change for 'perf trace' in that case is to do nothing, it work
as-is, we have just to fix the python binding to do that rename.
Perhaps we can live with that, to avoid having three different cases:
!nr, nr and __syscall_nr.
Ingo, Peter, have you guys followed this case?
Summary: Some tracepoint have multiple fields with the same name, 'nr',
the first one is a unique syscall ID, the other is a syscall
argument:
[root@...et ~]# cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_io_getevents/format
name: sys_enter_io_getevents
ID: 747
format:
field:unsigned short common_type; offset:0; size:2; signed:0;
field:unsigned char common_flags; offset:2; size:1; signed:0;
field:unsigned char common_preempt_count; offset:3; size:1; signed:0;
field:int common_pid; offset:4; size:4; signed:1;
field:int nr; offset:8; size:4; signed:1;
field:aio_context_t ctx_id; offset:16; size:8; signed:0;
field:long min_nr; offset:24; size:8; signed:0;
field:long nr; offset:32; size:8; signed:0;
field:struct io_event * events; offset:40; size:8; signed:0;
field:struct timespec * timeout; offset:48; size:8; signed:0;
print fmt: "ctx_id: 0x%08lx, min_nr: 0x%08lx, nr: 0x%08lx, events: 0x%08lx, timeout: 0x%08lx", ((unsigned long)(REC->ctx_id)), ((unsigned long)(REC->min_nr)), ((unsigned long)(REC->nr)), ((unsigned long)(REC->events)), ((unsigned long)(REC->timeout))
[root@...et ~]#
- Arnaldo
> field:unsigned short common_type; offset:0; size:2; signed:0;
> field:unsigned char common_flags; offset:2; size:1; signed:0;
> field:unsigned char common_preempt_count; offset:3; size:1; signed:0;
> field:int common_pid;offset:4;size:4;signed:1;
> field:int nr; offset:8; size:4; signed:1;
> field:aio_context_t ctx_id; offset:16; size:8; signed:0;
> field:long min_nr; offset:24; size:8; signed:0;
> field:long nr; offset:32; size:8; signed:0;
> field:struct io_event * events; offset:40; size:8; signed:0;
> field:struct timespec * timeout; offset:48; size:8; signed:0;
>
> print fmt: "ctx_id: 0x%08lx, min_nr: 0x%08lx, nr: 0x%08lx,
> events: 0x%08lx, timeout: 0x%08lx", ((unsigned long)(REC->ctx_id)),
> ((unsigned long)(REC->min_nr)), ((unsigned long)(REC->nr)),
> ((unsigned long)(REC->events)), ((unsigned long)(REC->timeout))
>
> As above 'int nr;' and 'long nr;' variables have
> duplicated name so problems are occurred in perf-script i.e.
>
> # perf record -e syscalls:*
> # perf script -g python
> # perf script -s perf-script.py
> File "perf-script.py", line 8694
> def syscalls__sys_enter_io_getevents(event_name, context, common_cpu,
> SyntaxError: duplicate argument 'nr' in function definition
> Error running python script perf-script.py
>
> As above, problems about duplicated argument occurred.
> Not only sys_enter_io_getevent() but also sys_enter_io_submit()
> have relevevance to this problem.
>
> So rename a variable 'nr' to '__syscall_nr' for system call number
> in print_syscall_enter() and etc.
>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Lai Jiangshan <jiangshanlai@...il.com>
> Signed-off-by: Taeung Song <treeze.taeung@...il.com>
> ---
> kernel/trace/trace.h | 4 ++--
> kernel/trace/trace_syscalls.c | 16 ++++++++--------
> 2 files changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 8414fa4..98b3c66 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -88,13 +88,13 @@ enum trace_type {
> */
> struct syscall_trace_enter {
> struct trace_entry ent;
> - int nr;
> + int __syscall_nr;
> unsigned long args[];
> };
>
> struct syscall_trace_exit {
> struct trace_entry ent;
> - int nr;
> + int __syscall_nr;
> long ret;
> };
>
> diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
> index 0655afb..90bb468 100644
> --- a/kernel/trace/trace_syscalls.c
> +++ b/kernel/trace/trace_syscalls.c
> @@ -118,7 +118,7 @@ print_syscall_enter(struct trace_iterator *iter, int flags,
> int i, syscall;
>
> trace = (typeof(trace))ent;
> - syscall = trace->nr;
> + syscall = trace->__syscall_nr;
> entry = syscall_nr_to_meta(syscall);
>
> if (!entry)
> @@ -164,7 +164,7 @@ print_syscall_exit(struct trace_iterator *iter, int flags,
> struct syscall_metadata *entry;
>
> trace = (typeof(trace))ent;
> - syscall = trace->nr;
> + syscall = trace->__syscall_nr;
> entry = syscall_nr_to_meta(syscall);
>
> if (!entry) {
> @@ -261,7 +261,7 @@ static int __init syscall_enter_define_fields(struct trace_event_call *call)
> int i;
> int offset = offsetof(typeof(trace), args);
>
> - ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
> + ret = trace_define_field(call, SYSCALL_FIELD(int, __syscall_nr), FILTER_OTHER);
> if (ret)
> return ret;
>
> @@ -281,7 +281,7 @@ static int __init syscall_exit_define_fields(struct trace_event_call *call)
> struct syscall_trace_exit trace;
> int ret;
>
> - ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
> + ret = trace_define_field(call, SYSCALL_FIELD(int, __syscall_nr), FILTER_OTHER);
> if (ret)
> return ret;
>
> @@ -332,7 +332,7 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
> return;
>
> entry = ring_buffer_event_data(event);
> - entry->nr = syscall_nr;
> + entry->__syscall_nr = syscall_nr;
> syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
>
> event_trigger_unlock_commit(trace_file, buffer, event, entry,
> @@ -378,7 +378,7 @@ static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
> return;
>
> entry = ring_buffer_event_data(event);
> - entry->nr = syscall_nr;
> + entry->__syscall_nr = syscall_nr;
> entry->ret = syscall_get_return_value(current, regs);
>
> event_trigger_unlock_commit(trace_file, buffer, event, entry,
> @@ -579,7 +579,7 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
> if (!rec)
> return;
>
> - rec->nr = syscall_nr;
> + rec->__syscall_nr = syscall_nr;
> syscall_get_arguments(current, regs, 0, sys_data->nb_args,
> (unsigned long *)&rec->args);
> perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
> @@ -652,7 +652,7 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
> if (!rec)
> return;
>
> - rec->nr = syscall_nr;
> + rec->__syscall_nr = syscall_nr;
> rec->ret = syscall_get_return_value(current, regs);
> perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
> }
> --
> 2.5.0
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