Date: Sun, 19 Feb 2017 11:31:44 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Hans Petter Selasky <hps@selasky.org> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: First thread in proc in not passed to thread_dtor eventhandler upon exit Message-ID: <20170219093144.GU2092@kib.kiev.ua> In-Reply-To: <060681c7-4c46-dcc7-d797-868fd0ad35a6@selasky.org> References: <933e132d-289b-330d-b349-584a25e279d4@selasky.org> <20170219035422.GQ2092@kib.kiev.ua> <060681c7-4c46-dcc7-d797-868fd0ad35a6@selasky.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sun, Feb 19, 2017 at 09:43:24AM +0100, Hans Petter Selasky wrote: > 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? Your patch is in-line with e.g. osd handling, so I do not see a reason to suggest a different approach. Looks fine. Of course, the only worry is the fact that event handlers are called for the thread which is not newly allocated nor just freed. > 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)
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20170219093144.GU2092>