From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4BC57405.1080403@domain.hid> Date: Wed, 14 Apr 2010 09:51:33 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <4B97BA0C.9000702@domain.hid> <1268472523.27899.135.camel@domain.hid> <4B9BB9B1.5050003@domain.hid> <1268498034.27899.167.camel@domain.hid> <4B9C2100.6090806@domain.hid> <1268584465.27899.197.camel@domain.hid> <4BB4F857.5020906@domain.hid> <4BB50C8B.2000405@domain.hid> <1270156940.2418.403.camel@domain.hid> <4BB50F7C.1020102@domain.hid> <1270157507.2418.409.camel@domain.hid> <4BB511C7.1050507@domain.hid> <1270158532.2418.420.camel@domain.hid> <4BB51631.5030609@domain.hid> <1270159246.2418.432.camel@domain.hid> <4BB51931.3080307@domain.hid> <4BB523E8.705@domain.hid> <4BB5250F.1040409@domain.hid> <4BB52769.4080702@domain.hid> <4BB5348B.2070805@domain.hid> <4BB5C95E.9060502@domain.hid> <4BB5D0D4.40908@domain.hid> <4BB5D1A0.8030007@domain.hid> <4BB5D4FB.4010901@domain.hid> <1271191271.2365.436.camel@domain.hid> <4BC4F8CA.4080202@domain.hid> <1271229750.2365.444.camel@domain.hid. org> <4BC570A4.1090203@domain.hid> In-Reply-To: <4BC570A4.1090203@domain.hid> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig321FC3F6D0B972065AC297E3" Sender: jan.kiszka@domain.hid Subject: Re: [Xenomai-core] [Xenomai-help] Analogy cmd_write example explanation List-Id: Xenomai life and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philippe Gerum Cc: Alexis Berlemont , xenomai-core This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig321FC3F6D0B972065AC297E3 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable Jan Kiszka wrote: > Philippe Gerum wrote: >> On Wed, 2010-04-14 at 01:05 +0200, Jan Kiszka wrote: >>> Philippe Gerum wrote: >>>> The steps now: >>>> >>>> - we implement the automatic switchback of shadow nrt threads to >>>> secondary mode, upon return from Xenomai (primary) syscalls. I am >>>> working on this. The most significant impact is on userland, due to = the >>>> fastsynch support, actually. Kernel-wise, it's rather straightforwar= d. >>>> The only exception to this would be when the caller owns an exclusiv= e >>>> resource (like a mutex), in which case the mode downgrade should be >>>> postponed until the syscall releasing the last resource held returns= =2E >>> Kernel is clear, but user space sounds indeed interesting. I guess we= >>> need an out-of-band channel to tell the kernel about pending >>> user-space-only lock ownerships when calling some unrelated syscall. = How >>> does your current approach look like? >> I want to keep things simple: shadow nrt will go through the syscalls >> for acquisition/release of owned resources, instead of fastsynchs. >=20 > Then I'll have to pick this up as that will very likely create unhappy > customers. In fact, the majority of our Xenomai threads are nrt (yeah, > that happens if you convert existing applications). Hmm, thinking about it again, there not that much to optimize in the trivial, non-nested locking case (on entry, we already go through the syscall if we aren't migrated yet, just the release syscall will be new). I will check what share of our load is nested and would actually suffer from unconditional syscalls. I just hope there is no issue with dropping the lazy scheme as that would complicate things in a way I would not want to go as well. Jan --------------enig321FC3F6D0B972065AC297E3 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iEYEARECAAYFAkvFdAkACgkQitSsb3rl5xR99ACdFMfMot2sRk1nZWKWxZ/miVOS ljwAn3Xsitv6jbNLIYlgr2660Shiii0s =oCLv -----END PGP SIGNATURE----- --------------enig321FC3F6D0B972065AC297E3--