Date: Sun, 19 Feb 2017 09:43:24 +0100 From: Hans Petter Selasky <hps@selasky.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: First thread in proc in not passed to thread_dtor eventhandler upon exit Message-ID: <060681c7-4c46-dcc7-d797-868fd0ad35a6@selasky.org> In-Reply-To: <20170219035422.GQ2092@kib.kiev.ua> References: <933e132d-289b-330d-b349-584a25e279d4@selasky.org> <20170219035422.GQ2092@kib.kiev.ua>
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On 02/19/17 04:54, Konstantin Belousov wrote:
> On Sat, Feb 18, 2017 at 10:40:00PM +0100, Hans Petter Selasky wrote:
>> Hi,
>>
>> 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?
--HPS
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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);
+ td = FIRST_THREAD_IN_PROC(p);
+ 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)
#endif
/* Free all OSD associated to this thread. */
osd_thread_exit(td);
+
+ /* 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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