On Sun, 10 Jun 2012 17:47:24 +0200, Sedat Dilek wrote:
Hi,
I see the same warning especially when resuming from a suspend (see
timestamps >=30-35sec) between Linux v3.5-rc1..v3.5-rc2.
$ sudo grep kvmclock.c /var/log/kern.log
Jun 4 21:11:32 fambox kernel: [ 784.037237] WARNING: at
arch/x86/kernel/kvmclock.c:127
kvm_check_and_clear_guest_paused+0x52/0x60()
Jun 5 20:35:57 fambox kernel: [ 1928.458060] WARNING: at
arch/x86/kernel/kvmclock.c:127
kvm_check_and_clear_guest_paused+0x52/0x60()
Jun 8 09:35:52 fambox kernel: [ 3290.134637] WARNING: at
arch/x86/kernel/kvmclock.c:127
kvm_check_and_clear_guest_paused+0x52/0x60()
Jun 8 09:35:52 fambox kernel: [ 3290.238592] WARNING: at
arch/x86/kernel/kvmclock.c:127
kvm_check_and_clear_guest_paused+0x52/0x60()
Jun 8 12:11:20 fambox kernel: [ 5777.023571] WARNING: at
arch/x86/kernel/kvmclock.c:127
kvm_check_and_clear_guest_paused+0x52/0x60()
Jun 9 13:32:50 fambox kernel: [ 2778.842695] WARNING: at
arch/x86/kernel/kvmclock.c:127
kvm_check_and_clear_guest_paused+0x52/0x60()
From [1]:
"...The warning itself is not required for the check_and_clear
function and can be removed as far as I am concerned."
From [2] commit 3b5d56b9317fa7b5407dff1aa7b115bf6cdbd494 ("kvmclock:
Add functions to check if the host has stopped the vm")
...
+bool kvm_check_and_clear_guest_paused(void)
+{
+ bool ret = false;
+ struct pvclock_vcpu_time_info *src;
+
+ /*
+ * per_cpu() is safe here because this function is only
called from
+ * timer functions where preemption is already disabled.
+ */
+ WARN_ON(!in_atomic());
+ src = &__get_cpu_var(hv_clock);
+ if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
+ __this_cpu_and(hv_clock.flags,
~PVCLOCK_GUEST_STOPPED);
+ ret = true;
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(kvm_check_and_clear_guest_paused);
+
...
( The export macro was dropped in a followup commit. )
So you mean "WARN_ON(!in_atomic());" can be deleted?
When I wrote the patch originally, I was under the (incorrect)
assumption that the watch dog was only ever reset in an atomic context.
Given that this is not the case, the warning can be removed. Though
before that happens, I have a question: if this is called outside of an
atomic context, is the use of __get_cpu_Var() and __this_cpu_and()
invalid?
Thanks,
Eric
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