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>

1 files changed, 14 insertions, 8 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index c73c4284160..1bd9e86fda1 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,