exec: Clarify "time_to_kill" behavior

Reported by John Quick.

(cherry picked from commit 5bc0c8f)

modules/exec/README

@@ -119,9 +119,18 @@ modparam("exec", "setvars", 1)
 
 1.3.2.  time_to_kill (integer)
 
-   Specifies the longest time (in seconds) that a program is
-   allowed to execute. Once this duration is exceeded, the program
-   is terminated (SIGTERM)
+   If set, this parameter specifies the longest time (in seconds)
+   that a program is allowed to execute. Once this duration is
+   exceeded, the program is terminated (SIGTERM).
+
+   NOTE: due to internal limitations, a SIGTERM will actually be
+   sent to all job pids once the "time_to_kill" expiration timeout
+   hits. On a standard system, this should have no side-effects,
+   as pids are monotonically increasing in a slow manner, and
+   OpenSIPS should run under the "opensips" user, thus rendering
+   it unable to terminate non-child processes. If this is not the
+   case on your system, do not use the OpenSIPS "time_to_kill"
+   feature -- rather implement it within your external app!
 
    Default value is 0 (disabled).
 

modules/exec/doc/exec_admin.xml

@@ -133,8 +133,19 @@ modparam("exec", "setvars", 1)
 			<varname>time_to_kill</varname> (integer)
 		</title>
 		<para>
-		Specifies the longest time (in seconds) that a program is allowed to
-		execute. Once this duration is exceeded, the program is terminated (SIGTERM)
+		If set, this parameter specifies the longest time (in seconds) that a
+		program is allowed to execute. Once this duration is exceeded, the
+		program is terminated (SIGTERM).
+		</para>
+		<para>
+		NOTE: due to internal limitations, a SIGTERM will actually be sent to
+		<emphasis role='bold'>all</emphasis> job pids once the "time_to_kill"
+		expiration timeout hits. On a standard system, this should have no
+		side-effects, as pids are monotonically increasing in a slow manner,
+		and OpenSIPS should run under the "opensips" user, thus rendering it
+		unable to terminate non-child processes. If this is not the case on
+		your system, do not use the OpenSIPS "time_to_kill" feature -- rather
+		implement it within your external app!
 		</para>
 		<para>
 		<emphasis>

modules/exec/kill.c

@@ -106,7 +106,7 @@ static void timer_routine(unsigned int ticks , void * attr)
 		tmp_tl=ret->next_tl;
 		ret->next_tl=ret->prev_tl=0;
 		if (ret->time_out>0) {
-			LM_INFO("exec timeout, pid %d -> sending SIGTERM\n", ret->pid);
+			LM_DBG("pid %d -> sending SIGTERM\n", ret->pid);
 			killr=kill(ret->pid, SIGTERM);
 			LM_DBG("child process (%d) kill status: %d\n", ret->pid, killr );
 		}