Re: [PATCH 1/2] tracing: let trace_signal_generate() report more info, kill overflow_fail/lose_info

Oleg Nesterov
2011-11-23T17:42:23Z

On 11/23, Li Zefan wrote:
>
> > /**
> > * signal_generate - called when a signal is generated
> > * @sig: signal number
> > * @info: pointer to struct siginfo
> > * @task: pointer to struct task_struct
> > + * @group: shared or private
> > + * @resutl: TRACE_SIGNAL_*
> > *
>
> s/resutl/result ;)

I'll send the bugreport to gcc.gnu.org. Surely -Wall should catch
such a typo!

------------------------------------------------------------------------------
[PATCH v2 1/2] tracing: let trace_signal_generate() report more info, kill overflow_fail/lose_info

Incompatible change.

__send_signal()->trace_signal_generate() doesn't report enough info.
The users want to know was the signal actually delivered or not, and
they also need the shared/private info.

The patch moves trace_signal_generate() at the end of __send_signal()
and adds the 2 additional arguments.

This also allows us to kill trace_signal_overflow_fail/lose_info, we
can simply add the appropriate TRACE_SIGNAL_ "result" codes.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
include/trace/events/signal.h | 85 +++++++++++------------------------------
kernel/signal.c | 22 +++++++----
2 files changed, 36 insertions(+), 71 deletions(-)

diff --git a/include/trace/events/signal.h b/include/trace/events/signal.h
index 17df434..2de7208 100644
--- a/include/trace/events/signal.h
+++ b/include/trace/events/signal.h
@@ -23,11 +23,23 @@
} \
} while (0)

+#ifndef TRACE_HEADER_MULTI_READ
+enum {
+ TRACE_SIGNAL_DELIVERED,
+ TRACE_SIGNAL_IGNORED,
+ TRACE_SIGNAL_ALREADY_PENDING,
+ TRACE_SIGNAL_OVERFLOW_FAIL,
+ TRACE_SIGNAL_LOSE_INFO,
+};
+#endif
+
/**
* signal_generate - called when a signal is generated
* @sig: signal number
* @info: pointer to struct siginfo
* @task: pointer to struct task_struct
+ * @group: shared or private
+ * @result: TRACE_SIGNAL_*
*
* Current process sends a 'sig' signal to 'task' process with
* 'info' siginfo. If 'info' is SEND_SIG_NOINFO or SEND_SIG_PRIV,
@@ -37,9 +49,10 @@
*/
TRACE_EVENT(signal_generate,

- TP_PROTO(int sig, struct siginfo *info, struct task_struct *task),
+ TP_PROTO(int sig, struct siginfo *info, struct task_struct *task,
+ int group, int result),

- TP_ARGS(sig, info, task),
+ TP_ARGS(sig, info, task, group, result),

TP_STRUCT__entry(
__field( int, sig )
@@ -47,6 +60,8 @@ TRACE_EVENT(signal_generate,
__field( int, code )
__array( char, comm, TASK_COMM_LEN )
__field( pid_t, pid )
+ __field( int, group )
+ __field( int, result )
),

TP_fast_assign(
@@ -54,11 +69,14 @@ TRACE_EVENT(signal_generate,
TP_STORE_SIGINFO(__entry, info);
memcpy(__entry->comm, task->comm, TASK_COMM_LEN);
__entry->pid = task->pid;
+ __entry->group = group;
+ __entry->result = result;
),

- TP_printk("sig=%d errno=%d code=%d comm=%s pid=%d",
+ TP_printk("sig=%d errno=%d code=%d comm=%s pid=%d grp=%d res=%d",
__entry->sig, __entry->errno, __entry->code,
- __entry->comm, __entry->pid)
+ __entry->comm, __entry->pid, __entry->group,
+ __entry->result)
);

/**
@@ -101,65 +119,6 @@ TRACE_EVENT(signal_deliver,
__entry->sa_handler, __entry->sa_flags)
);

-DECLARE_EVENT_CLASS(signal_queue_overflow,
-
- TP_PROTO(int sig, int group, struct siginfo *info),
-
- TP_ARGS(sig, group, info),
-
- TP_STRUCT__entry(
- __field( int, sig )
- __field( int, group )
- __field( int, errno )
- __field( int, code )
- ),
-
- TP_fast_assign(
- __entry->sig = sig;
- __entry->group = group;
- TP_STORE_SIGINFO(__entry, info);
- ),
-
- TP_printk("sig=%d group=%d errno=%d code=%d",
- __entry->sig, __entry->group, __entry->errno, __entry->code)
-);
-
-/**
- * signal_overflow_fail - called when signal queue is overflow
- * @sig: signal number
- * @group: signal to process group or not (bool)
- * @info: pointer to struct siginfo
- *
- * Kernel fails to generate 'sig' signal with 'info' siginfo, because
- * siginfo queue is overflow, and the signal is dropped.
- * 'group' is not 0 if the signal will be sent to a process group.
- * 'sig' is always one of RT signals.
- */
-DEFINE_EVENT(signal_queue_overflow, signal_overflow_fail,
-
- TP_PROTO(int sig, int group, struct siginfo *info),
-
- TP_ARGS(sig, group, info)
-);
-
-/**
- * signal_lose_info - called when siginfo is lost
- * @sig: signal number
- * @group: signal to process group or not (bool)
- * @info: pointer to struct siginfo
- *
- * Kernel generates 'sig' signal but loses 'info' siginfo, because siginfo
- * queue is overflow.
- * 'group' is not 0 if the signal will be sent to a process group.
- * 'sig' is always one of non-RT signals.
- */
-DEFINE_EVENT(signal_queue_overflow, signal_lose_info,
-
- TP_PROTO(int sig, int group, struct siginfo *info),
-
- TP_ARGS(sig, group, info)
-);
-
#endif /* _TRACE_SIGNAL_H */

/* This part must be outside protection */
diff --git a/kernel/signal.c b/kernel/signal.c
index b3f78d0..5f130f6 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1025,13 +1025,13 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
struct sigpending *pending;
struct sigqueue *q;
int override_rlimit;
-
- trace_signal_generate(sig, info, t);
+ int ret = 0, result;

assert_spin_locked(&t->sighand->siglock);

+ result = TRACE_SIGNAL_IGNORED;
if (!prepare_signal(sig, t, from_ancestor_ns))
- return 0;
+ goto ret;

pending = group ? &t->signal->shared_pending : &t->pending;
/*
@@ -1039,8 +1039,11 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
* exactly one non-rt signal, so that we can get more
* detailed information about the cause of the signal.
*/
+ result = TRACE_SIGNAL_ALREADY_PENDING;
if (legacy_queue(pending, sig))
- return 0;
+ goto ret;
+
+ result = TRACE_SIGNAL_DELIVERED;
/*
* fast-pathed signals for kernel-internal things like SIGSTOP
* or SIGKILL.
@@ -1095,14 +1098,15 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
* signal was rt and sent by user using something
* other than kill().
*/
- trace_signal_overflow_fail(sig, group, info);
- return -EAGAIN;
+ result = TRACE_SIGNAL_OVERFLOW_FAIL;
+ ret = -EAGAIN;
+ goto ret;
} else {
/*
* This is a silent loss of information. We still
* send the signal, but the *info bits are lost.
*/
- trace_signal_lose_info(sig, group, info);
+ result = TRACE_SIGNAL_LOSE_INFO;
}
}

@@ -1110,7 +1114,9 @@ out_set:
signalfd_notify(t, sig);
sigaddset(&pending->signal, sig);
complete_signal(sig, t, group);
- return 0;
+ret:
+ trace_signal_generate(sig, info, t, group, result);
+ return ret;
}

static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
--
1.5.5.1