From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Bader Subject: Re: Strange PVM spinlock case revisited Date: Wed, 13 Feb 2013 13:16:51 +0100 Message-ID: <511B8433.7070006@canonical.com> References: <51151ABF.1070007@canonical.com> <1360603744.20449.74.camel@zakaz.uk.xensource.com> <511B7983.7000907@canonical.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============4618302985902255805==" Return-path: In-Reply-To: <511B7983.7000907@canonical.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: Andrew Cooper , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --===============4618302985902255805== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="------------enigB9D27EE82D4922A87EF8074A" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigB9D27EE82D4922A87EF8074A Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 13.02.2013 12:31, Stefan Bader wrote: > I will try to think of some better way. Not sure the thinking is realis= tic but > maybe that could happen: >=20 > xen_spin_lock_slow(a) > ... > enables irq and upcalls are pending > upcall processing wants lock b > xen_spin_lock_slow(b) > --- just before replacing lock_spinners --- > xen_spin_unlock_slow= (a) > finds other vcpu, tr= iggers > IRQ > lock b is top spinner > going into poll_irq > poll_irq returns > lock a gets restored > so maybe no spinners on b > dropping out to xen_spin_lock > unlock of b not findi= ng any > spinners > lock b acquired >=20 > That way the irq for lock a maybe get lost... Darn, maybe not since the pending status is not cleared when leaving xen_spin_lock_slow. So I assume the interrupted lock does at least one cy= cle out of slow and back... --------------enigB9D27EE82D4922A87EF8074A Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with undefined - http://www.enigmail.net/ iQIcBAEBCgAGBQJRG4QzAAoJEOhnXe7L7s6jFEQP+wVJZ7p82/Km3V8LAj+IYYR+ m03HBcD3nj/sBX8j3Qd+CtQqFwQwxSS7PqtnMlleYIi6uqBdVvilzh6pJ+I7Wk3V 6LEVg8im+yQduBLhtSTEUATo34IYM8ep4g7qs7rgV4AHJqz4Zpq8RVCBWNltPtP8 yL0fZR0rvqvoReKg82M4CHb9Ph/ZXC4kUDvY9KhtMcEoMFSQaPhdKA2pNQI/OoHi 5cEs52zxaxXw2Ig/MrU3EIzdr5rKLBdeFwmikWnte0j7+11yb4zg8uIidZv0I6zp 8tVKdt5VH5Z595RkK7gCr+zCPx1WbmzAP4vKfR6F4gq/XSSNon63bmZdzAsIviEj cz5z2hp6eH/36eD2CyorEbyzES70K0vIjJViE/ka6oAmoGrccz9H41a5XRpt/Vwx z9NuS1E/LtcCAMrxcXyfq6Gdt+BW9HlnXvSxQzc2omCGwOszKDCXjnoLtRm5kIDp SAU/94x1OBkZ+2bDVf/sBS3jWDagA87iIOa0+c7iu9QmyTPKD3F4gcYGxmUd8gEd q5oclIYlEuJqo30Z1Nc0v45/1POrI4p8TQNZ8i2oOzqLZrj3ivggsRNEuV3YvelW ZMgwiLH1Fy/ut+AxuWs4fMRXuYg34a+yrW2fCMky2tzUjFV3E6a2h07SpmeQKhAA eF4HvVYQh361ziMueAgu =Vj3/ -----END PGP SIGNATURE----- --------------enigB9D27EE82D4922A87EF8074A-- --===============4618302985902255805== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel --===============4618302985902255805==--