tracing: let trace_signal_generate() report more info, kill overflow_fail/lose_info

__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.

Reported-by: Seiji Aguchi <saguchi@redhat.com>
Reviewed-by: Seiji Aguchi <seiji.aguchi@hds.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>

2 files changed, 36 insertions, 71 deletions

diff --git a/include/trace/events/signal.h b/include/trace/events/signal.h
index 17df43464df0..39a8a430d90f 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 c73c4284160e..1bd9e86fda1f 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1054,13 +1054,13 @@ 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;
         /*
@@ -1068,8 +1068,11 @@ 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.
@@ -1127,14 +1130,15 @@ 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;
                 }
         }
 
@@ -1142,7 +1146,9 @@ 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,