[PATCH -tip v3 3/3] tracepoint: Add signal loss events

Masami Hiramatsu
2009-11-20T21:29:24Z

Add signal_overflow_fail and signal_lose_info tracepoints
for signal-lost events.

Changes in v3:
- Add docbook style comments

Changes in v2:
- Use siginfo string macro

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Suggested-by: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
---

include/trace/events/signal.h | 68 +++++++++++++++++++++++++++++++++++++++++
kernel/signal.c | 19 ++++++++---
2 files changed, 82 insertions(+), 5 deletions(-)

diff --git a/include/trace/events/signal.h b/include/trace/events/signal.h
index ddf89c9..8404d8b 100644
--- a/include/trace/events/signal.h
+++ b/include/trace/events/signal.h
@@ -99,6 +99,74 @@ TRACE_EVENT(signal_deliver,
__entry->sig, __entry->errno, __entry->code,
__entry->sa_handler, __entry->sa_flags)
);
+
+/**
+ * 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.
+ */
+TRACE_EVENT(signal_overflow_fail,
+
+ 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_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.
+ */
+TRACE_EVENT(signal_lose_info,
+
+ 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)
+);
#endif /* _TRACE_SIGNAL_H */

/* This part must be outside protection */
diff --git a/kernel/signal.c b/kernel/signal.c
index d518984..6b982f2 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -919,12 +919,21 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
break;
}
} else if (!is_si_special(info)) {
- if (sig >= SIGRTMIN && info->si_code != SI_USER)
- /*
- * Queue overflow, abort. We may abort if the signal was rt
- * and sent by user using something other than kill().
- */
+ if (sig >= SIGRTMIN && info->si_code != SI_USER) {
+ /*
+ * Queue overflow, abort. We may abort if the
+ * signal was rt and sent by user using something
+ * other than kill().
+ */
+ trace_signal_overflow_fail(sig, group, info);
return -EAGAIN;
+ } 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);
+ }
}