From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4B5CD1E3.5070809@domain.hid> Date: Mon, 25 Jan 2010 00:04:03 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <4B5B02E3.8060103@domain.hid> <4B5CCF35.2040402@domain.hid> In-Reply-To: <4B5CCF35.2040402@domain.hid> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig2F7F719B0972BAE62EB12815" Sender: jan.kiszka@domain.hid Subject: Re: [Xenomai-core] [Adeos-main] [RFC][PATCH] x86: Fix root domain state restoring on exception return List-Id: Xenomai life and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: Jan Kiszka , adeos-main , xenomai-core , Wolfgang Mauerer This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig2F7F719B0972BAE62EB12815 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Gilles Chanteperdrix wrote: > Jan Kiszka wrote: >> If we enter __ipipe_handle_exception over a non-root domain and leave = it >> due to migration in the event handler over root, we must not restore t= he >> root domain state so far saved on entry. This caused subtle pipeline >> state corruptions. Actually, we only need to save the state if we ente= r >> over the root domain and have to align its state to the hardware >> interrupt mask. >> >> Moreover, the x86-32 regs.eflags fix-up must happen based on the curre= nt >> root domain state to avoid more spurious corruptions. >> >> Signed-off-by: Jan Kiszka >> --- >> >> This patch is so far running fine on the x86-64 boxes of our colleague= s >> @Healthcare. It currently makes most sense to me, also for (untested) >> x86-32, but maybe I'm still missing a problematic scenario. >> >> arch/x86/kernel/ipipe.c | 64 ++++++++++++++++++++++++++------------= -------- >> 1 files changed, 36 insertions(+), 28 deletions(-) >> >> diff --git a/arch/x86/kernel/ipipe.c b/arch/x86/kernel/ipipe.c >> index 4442d96..8253993 100644 >> --- a/arch/x86/kernel/ipipe.c >> +++ b/arch/x86/kernel/ipipe.c >> @@ -702,19 +702,17 @@ static int __ipipe_xlate_signo[] =3D { >> =20 >> int __ipipe_handle_exception(struct pt_regs *regs, long error_code, i= nt vector) >> { >> - unsigned long flags; >> - >> - /* Pick up the root domain state of the interrupted context. */ >> - local_save_flags(flags); >> + bool restore_flags =3D false; >> + unsigned long flags =3D 0; >> =20 >> - if (ipipe_root_domain_p) { >> + if (ipipe_root_domain_p && irqs_disabled_hw()) { >=20 > I really do not understand this hunk. It differs a lot from the current= > situation. In the current situation __fixup_if really does something, > even if irqs were not masked on entry. >=20 This hunk is no longer related to __fixup_if. The latter now picks up the information about what to fix from root domain state _after_ the return of the ipipe exception hook. That way we avoid leaking the wrong root state on entry over a non-root domain after migration within the hoo= k. Jan --------------enig2F7F719B0972BAE62EB12815 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 iEYEARECAAYFAktc0eMACgkQitSsb3rl5xQ9BQCgrVmEH04FbXBLi2Ko8ULQHING krMAoIsfkna3+6cy9Pr1uV9GGTQwAV/m =Gu1Q -----END PGP SIGNATURE----- --------------enig2F7F719B0972BAE62EB12815--