David Lively
2007-Jun-25 18:41 UTC
[Xen-devel] ignoring xenbus state transitions during shutdown
Hi Folks -
In otherend_changed() in xenbus_probe.c, the driver is trying to
ignore xenbus state transitions while the guest OS is shutting down. It
currently does this by looking for system_state > SYSTEM_RUNNING. But
system_state is not exported by some kernels that use it (e.g., SLES9
running in a HVM guest), so the xenbus driver can''t be loaded.
The comments indicate we''re trying to avoid a failure that occurs
when
there is no rootfs. I haven''t yet seen this failure (after removing
the
code my shutdowns with PV drivers seemed to work fine, though I haven''t
pushed hard yet), but I suspect I shouldn''t be ignoring it. I was
thinking it might be better to test for the screw condition (no rootfs)
directly, perhaps something like try vfs_stat("/", &stat) and see
whether it fails (??). (These state transitions are relatively rare, so
it doesn''t need to be a particularly cheap test.)
Any other suggestions? I''ve heard of the old global
''system_running'',
but that''s not used SLES9, at least.
Thanks in Advance,
Dave
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Keir Fraser
2007-Jun-25 18:47 UTC
Re: [Xen-devel] ignoring xenbus state transitions during shutdown
Unless you care about domU kexec, you can pretty safely remove that system_state() check, so long as you remove the .shutdown callback hooks (in the same file) too. -- Keir On 25/6/07 19:41, "David Lively" <dlively@virtualiron.com> wrote:> Hi Folks - > In otherend_changed() in xenbus_probe.c, the driver is trying to > ignore xenbus state transitions while the guest OS is shutting down. It > currently does this by looking for system_state > SYSTEM_RUNNING. But > system_state is not exported by some kernels that use it (e.g., SLES9 > running in a HVM guest), so the xenbus driver can''t be loaded. > The comments indicate we''re trying to avoid a failure that occurs when > there is no rootfs. I haven''t yet seen this failure (after removing the > code my shutdowns with PV drivers seemed to work fine, though I haven''t > pushed hard yet), but I suspect I shouldn''t be ignoring it. I was > thinking it might be better to test for the screw condition (no rootfs) > directly, perhaps something like try vfs_stat("/", &stat) and see > whether it fails (??). (These state transitions are relatively rare, so > it doesn''t need to be a particularly cheap test.) > Any other suggestions? I''ve heard of the old global ''system_running'', > but that''s not used SLES9, at least. > > Thanks in Advance, > Dave > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
David Lively
2007-Jun-25 20:28 UTC
Re: [Xen-devel] ignoring xenbus state transitions during shutdown
Ok -- the .shutdown callbacks are there for Linux kernels >= 2.6.16. So I think I want to protect this (ignore transitions) code with: #if defined(CONFIG_KEXEC) || LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,16) (That is, ignore state transitions if kexec is enabled or if we''re defining the shutdown callbacks.) Right? (Or should I instead test only for CONFIG_KEXEC there and leave the shutdown callbacks NULL unless KEXEC is enabled?? Either way works for the cases I care about.) Dave Keir Fraser wrote:> Unless you care about domU kexec, you can pretty safely remove that > system_state() check, so long as you remove the .shutdown callback hooks (in > the same file) too. > > -- Keir > > On 25/6/07 19:41, "David Lively" <dlively@virtualiron.com> wrote: > > >> Hi Folks - >> In otherend_changed() in xenbus_probe.c, the driver is trying to >> ignore xenbus state transitions while the guest OS is shutting down. It >> currently does this by looking for system_state > SYSTEM_RUNNING. But >> system_state is not exported by some kernels that use it (e.g., SLES9 >> running in a HVM guest), so the xenbus driver can''t be loaded. >> The comments indicate we''re trying to avoid a failure that occurs when >> there is no rootfs. I haven''t yet seen this failure (after removing the >> code my shutdowns with PV drivers seemed to work fine, though I haven''t >> pushed hard yet), but I suspect I shouldn''t be ignoring it. I was >> thinking it might be better to test for the screw condition (no rootfs) >> directly, perhaps something like try vfs_stat("/", &stat) and see >> whether it fails (??). (These state transitions are relatively rare, so >> it doesn''t need to be a particularly cheap test.) >> Any other suggestions? I''ve heard of the old global ''system_running'', >> but that''s not used SLES9, at least. >> >> Thanks in Advance, >> Dave >> >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xensource.com >> http://lists.xensource.com/xen-devel >> > >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2007-Jun-25 20:39 UTC
Re: [Xen-devel] ignoring xenbus state transitions during shutdown
Only need #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,16). If the shutdown hooks aren''t defined then we won''t be causing xenbus state transitions when we shut down, kexec or not. -- Keir On 25/6/07 21:28, "David Lively" <dlively@virtualiron.com> wrote:> Ok -- the .shutdown callbacks are there for Linux kernels >= 2.6.16. > So I think I want to protect this (ignore transitions) code with: > #if defined(CONFIG_KEXEC) || LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,16) > > (That is, ignore state transitions if kexec is enabled or if we''re > defining the shutdown callbacks.) > > Right? (Or should I instead test only for CONFIG_KEXEC there and leave > the shutdown callbacks NULL unless KEXEC is enabled?? Either way works > for the cases I care about.) > > Dave > > Keir Fraser wrote: >> Unless you care about domU kexec, you can pretty safely remove that >> system_state() check, so long as you remove the .shutdown callback hooks (in >> the same file) too. >> >> -- Keir >> >> On 25/6/07 19:41, "David Lively" <dlively@virtualiron.com> wrote: >> >> >>> Hi Folks - >>> In otherend_changed() in xenbus_probe.c, the driver is trying to >>> ignore xenbus state transitions while the guest OS is shutting down. It >>> currently does this by looking for system_state > SYSTEM_RUNNING. But >>> system_state is not exported by some kernels that use it (e.g., SLES9 >>> running in a HVM guest), so the xenbus driver can''t be loaded. >>> The comments indicate we''re trying to avoid a failure that occurs when >>> there is no rootfs. I haven''t yet seen this failure (after removing the >>> code my shutdowns with PV drivers seemed to work fine, though I haven''t >>> pushed hard yet), but I suspect I shouldn''t be ignoring it. I was >>> thinking it might be better to test for the screw condition (no rootfs) >>> directly, perhaps something like try vfs_stat("/", &stat) and see >>> whether it fails (??). (These state transitions are relatively rare, so >>> it doesn''t need to be a particularly cheap test.) >>> Any other suggestions? I''ve heard of the old global ''system_running'', >>> but that''s not used SLES9, at least. >>> >>> Thanks in Advance, >>> Dave >>> >>> >>> _______________________________________________ >>> Xen-devel mailing list >>> Xen-devel@lists.xensource.com >>> http://lists.xensource.com/xen-devel >>> >> >> > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel