From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4E1C87BB.7000307@domain.hid> Date: Tue, 12 Jul 2011 19:43:23 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <4E1B469A.8000703@domain.hid> <4E1B4AC0.80506@domain.hid> <4E1B4C19.2070205@domain.hid> <4E1B542B.2010906@domain.hid> <4E1B5638.1050005@domain.hid> <4E1B56E0.20109@domain.hid> <4E1B57D1.1070401@domain.hid> <4E1B5860.1000309@domain.hid> <4E1B5944.5030408@domain.hid> <4E1BEC9F.1020404@domain.hid> <4E1BF619.6010609@domain.hid> <4E1C2912.9050605@domain.hid> <4E1C2959.8080004@domain.hid> <4E1C2A2D.9090602@domain.hid> <4E1C2AA5.6060208@domain.hid> <4E1C2B44.5060907@domain.hid> <4E1C2B8F.5080700@domain.hid> <4E1C2F56.8020103@domain.hid> <4E1C302A.8050309@domain.hid> <4E1C3301.2030203@domain.hid> <4E1C3672.1030104@domain.hid> <4E1C36EE.70803@domain.hid> <4E1C38CE.7090202@domain.hid> <4E1C3A5D.3020700@domain.hid> <4E1C44B4.50106@domain.hid> <4E1C8508.5010400@domain.hid> <4E1C858A.7070403@domain.hid> <4E1C86A1.6030707@domain.hid> In-Reply-To: <4E1C86A1.6030707@domain.hid> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig36BCFD142998D49D5C55870C" Sender: jan.kiszka@domain.hid Subject: Re: [Xenomai-core] [Xenomai-git] Jan Kiszka : nucleus: Fix race between gatekeeper and thread deletion List-Id: Xenomai life and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: Xenomai core This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig36BCFD142998D49D5C55870C Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 2011-07-12 19:38, Gilles Chanteperdrix wrote: > On 07/12/2011 07:34 PM, Jan Kiszka wrote: >> On 2011-07-12 19:31, Gilles Chanteperdrix wrote: >>> On 07/12/2011 02:57 PM, Jan Kiszka wrote: >>>> xnlock_put_irqrestore(&nklock, s); >>>> xnpod_schedule(); >>>> } >>>> @@ -1036,6 +1043,7 @@ redo: >>>> * to process this signal anyway. >>>> */ >>>> if (rthal_current_domain =3D=3D rthal_root_domain) { >>>> + XENO_BUGON(NUCLEUS, xnthread_test_info(thread, XNATOMIC)); >>> >>> Misleading dead code again, XNATOMIC is cleared not ten lines above. >> >> Nope, I forgot to remove that line. >> >>> >>>> if (XENO_DEBUG(NUCLEUS) && (!signal_pending(this_task) >>>> || this_task->state !=3D TASK_RUNNING)) >>>> xnpod_fatal >>>> @@ -1044,6 +1052,8 @@ redo: >>>> return -ERESTARTSYS; >>>> } >>>> =20 >>>> + xnthread_clear_info(thread, XNATOMIC); >>> >>> Why this? I find the xnthread_clear_info(XNATOMIC) right at the right= >>> place at the point it currently is. >> >> Nope. Now we either clear XNATOMIC after successful migration or when >> the signal is about to be sent (ie. in the hook). That way we can test= >> more reliably (TM) in the gatekeeper if the thread can be migrated. >=20 > Ok for adding the XNATOMIC test, because it improves the robustness, bu= t > why changing the way XNATOMIC is set and clear? Chances of breaking > thing while changing code in this area are really high... The current code is (most probably) broken as it does not properly synchronizes the gatekeeper against a signaled and "runaway" target Linux task. We need an indication if a Linux signal will (or already has) woken up the to-be-migrated task. That task may have continued over its context, potentially on a different CPU. Providing this indication is the purpose of changing where XNATOMIC is cleared. Jan --------------enig36BCFD142998D49D5C55870C Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk4ch7sACgkQitSsb3rl5xQxqgCePDEydKYJDBgH7TDzkdd5CKr9 Sj4Amwfdt9sCQT/BJRgt0k1WCRBryn9C =6t8q -----END PGP SIGNATURE----- --------------enig36BCFD142998D49D5C55870C--