tracepoint: Add signal deliver event

Add a tracepoint where a process gets a signal. This tracepoint
shows signal-number, sa-handler and sa-flag.

Changes in v3:
 - Add docbook style comments

Changes in v2:
 - Add siginfo argument
 - Fix comment

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Reviewed-by: Jason Baron <jbaron@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Oleg Nesterov <oleg@redhat.com>
LKML-Reference: <20091124215651.30449.20926.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 42 insertions, 0 deletions

diff --git a/include/trace/events/signal.h b/include/trace/events/signal.h
index ef51756a801d..a6d71de0dc0d 100644
--- a/include/trace/events/signal.h
+++ b/include/trace/events/signal.h
@@ -60,6 +60,45 @@ TRACE_EVENT(signal_generate,
                   __entry->comm, __entry->pid)
 );
 
+/**
+ * signal_deliver - called when a signal is delivered
+ * @sig: signal number
+ * @info: pointer to struct siginfo
+ * @ka: pointer to struct k_sigaction
+ *
+ * A 'sig' signal is delivered to current process with 'info' siginfo,
+ * and it will be handled by 'ka'. ka->sa.sa_handler can be SIG_IGN or
+ * SIG_DFL.
+ * Note that some signals reported by signal_generate tracepoint can be
+ * lost, ignored or modified (by debugger) before hitting this tracepoint.
+ * This means, this can show which signals are actually delivered, but
+ * matching generated signals and delivered signals may not be correct.
+ */
+TRACE_EVENT(signal_deliver,
+
+        TP_PROTO(int sig, struct siginfo *info, struct k_sigaction *ka),
+
+        TP_ARGS(sig, info, ka),
+
+        TP_STRUCT__entry(
+                __field(        int,            sig             )
+                __field(        int,            errno           )
+                __field(        int,            code            )
+                __field(        unsigned long,  sa_handler      )
+                __field(        unsigned long,  sa_flags        )
+        ),
+
+        TP_fast_assign(
+                __entry->sig    = sig;
+                TP_STORE_SIGINFO(__entry, info);
+                __entry->sa_handler     = (unsigned long)ka->sa.sa_handler;
+                __entry->sa_flags       = ka->sa.sa_flags;
+        ),
+
+        TP_printk("sig=%d errno=%d code=%d sa_handler=%lx sa_flags=%lx",
+                  __entry->sig, __entry->errno, __entry->code,
+                  __entry->sa_handler, __entry->sa_flags)
+);
 #endif /* _TRACE_SIGNAL_H */
 
 /* This part must be outside protection */
diff --git a/kernel/signal.c b/kernel/signal.c
index a1e0cc6b32c3..349d44937406 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1840,6 +1840,9 @@ relock:
                         ka = &sighand->action[signr-1];
                 }
 
+                /* Trace actually delivered signals. */
+                trace_signal_deliver(signr, info, ka);
+
                 if (ka->sa.sa_handler == SIG_IGN) /* Do nothing.  */
                         continue;
                 if (ka->sa.sa_handler != SIG_DFL) {