Messages in this thread | | | Date | Wed, 10 Aug 2011 10:36:39 +0100 | From | "Jan Beulich" <> | Subject | Re: [PATCH] x86, efi: Don't recursively acquire rtc_lock |
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>>> On 10.08.11 at 11:03, Ingo Molnar <mingo@elte.hu> wrote:
> * Jan Beulich <JBeulich@novell.com> wrote: > >> >>> On 08.08.11 at 15:40, Matt Fleming <matt@console-pimps.org> wrote: >> > On Fri, 2011-08-05 at 18:04 +0100, Jan Beulich wrote: >> >> >> >> Virtual platforms will have to take care of the serialization in the >> >> host anyway, so the guest side implementation of getwallclock et al >> >> is entirely unaffected. >> > >> > Ah, OK, that's the important part. I didn't realise that rtc_lock isn't >> > actually required by any other code. In which case, yes, it completely >> > makes sense to push the locking of rtc_lock down into the >> > implementations that actually need it. >> > >> > It'd be great if I could get some ACK's from the virtualization guys. >> > >> > --------8<-------- >> > >> > From a0a39dbb69f6ac675846bf00f30ad153506a4567 Mon Sep 17 00:00:00 2001 >> > From: Matt Fleming <matt.fleming@intel.com> >> > Date: Mon, 8 Aug 2011 12:59:35 +0100 >> > Subject: [PATCH] x86, efi: Don't recursively acquire rtc_lock >> > >> > A deadlock was introduced on x86 in commit ef68c8f87ed1 ("x86: >> > Serialize EFI time accesses on rtc_lock") because efi_get_time() and >> > friends can be called with rtc_lock already held by >> > read_persistent_time(), e.g. >> > >> > timekeeping_init() >> > read_persistent_clock() <-- acquire rtc_lock >> > efi_get_time() >> > phys_efi_get_time() <-- acquire rtc_lock <DEADLOCK> >> > >> > To fix this let's push the locking down into the get_wallclock() and >> > set_wallclock() implementations. Only the clock implementations that >> > access the x86 RTC directly need to acquire rtc_lock, so it makes >> > sense to push the locking down into the rtc, vrtc and efi code. >> > >> > The virtualization implementations don't require rtc_lock to be held >> > because they provide their own serialization. >> > >> > Signed-off-by: Matt Fleming <matt.fleming@intel.com> >> >> Acked-by: Jan Beulich <jbeulich@novell.com> > > How urgent is thix fix - can it wait until Thomas comes back and > starts processing patches again?
Without it booting on EFI can't be expected to work (and while I was really sure I tested this before submitting, I apparently must have used a stale kernel then - I'm really sorry for that), so getting it applied soon would be rather desirable.
But then again I don't seem to be able to boot 3.0.1 with both patches applied on my only EFI box, so there must be something else that broke, and hence maybe I really did test it (on 3.0-rc7) and it worked then. Debugging...
Jan
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