On 02/19/17 04:54, Konstantin Belousov wrote:
On Sat, Feb 18, 2017 at 10:40:00PM +0100, Hans Petter Selasky wrote:

Is the following a bug or feature. I observe that the first thread in a
procedure is not passed to thread_dtor as declared by the following
eventhandler, when the procedure exits.

EVENTHANDLER_DECLARE(thread_dtor, thread_dtor_fn);

Is this a bug or feature?
This is a feature.  When a zombie process is reaped, the last thread in
the process (the one which exited it) is left in the process thread list.
This is an optimization, because process without at least one thread
is never useful.

You can see the code in fork1() which allocates struct proc from zone
and then checks if there any thread pre-allocated as well (both struct
proc and struct thread are type-stable).

Since the last thread is not freed, its destructor is not signalled.

Hi Konstantin,

I see. To avoid leakage of LinuxKPI, Linux and Dtrace resources to all system threads, I think the attached patch is required. What do you think about the attached patch? If you don't like it can you suggest another approach?

diff --git a/sys/kern/kern_proc.c b/sys/kern/kern_proc.c
index f39326f..a206a0a 100644
--- a/sys/kern/kern_proc.c
+++ b/sys/kern/kern_proc.c
@@ -191,11 +191,17 @@ static int
 proc_ctor(void *mem, int size, void *arg, int flags)
 	struct proc *p;
+	struct thread *td;
 	p = (struct proc *)mem;
 	SDT_PROBE4(proc, , ctor , entry, p, size, arg, flags);
 	EVENTHANDLER_INVOKE(process_ctor, p);
 	SDT_PROBE4(proc, , ctor , return, p, size, arg, flags);
+	if (td != NULL) {
+		/* Make sure all thread constructors are executed */
+		EVENTHANDLER_INVOKE(thread_ctor, td);
+	}
 	return (0);
@@ -220,6 +226,9 @@ proc_dtor(void *mem, int size, void *arg)
 		/* Free all OSD associated to this thread. */
+		/* Make sure all thread destructors are executed */
+		EVENTHANDLER_INVOKE(thread_dtor, td);
 	EVENTHANDLER_INVOKE(process_dtor, p);
 	if (p->p_ksi != NULL)
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