On Tue, 16 Apr 2013, Konrad Rzeszutek Wilk wrote:
> When we online the CPU, we get this splat:
>
> smpboot: Booting Node 0 Processor 1 APIC 0x2
> installing Xen timer for CPU 1
> BUG: sleeping function called from invalid context at /home/konrad/ssd/konrad/linux/mm/slab.c:3179
> in_atomic(): 1, irqs_disabled(): 0, pid: 0, name: swapper/1
> Pid: 0, comm: swapper/1 Not tainted 3.9.0-rc6upstream-00001-g3884fad #1
> Call Trace:
> [<ffffffff810c1fea>] __might_sleep+0xda/0x100
> [<ffffffff81194617>] __kmalloc_track_caller+0x1e7/0x2c0
> [<ffffffff81303758>] ? kasprintf+0x38/0x40
> [<ffffffff813036eb>] kvasprintf+0x5b/0x90
> [<ffffffff81303758>] kasprintf+0x38/0x40
> [<ffffffff81044510>] xen_setup_timer+0x30/0xb0
> [<ffffffff810445af>] xen_hvm_setup_cpu_clockevents+0x1f/0x30
> [<ffffffff81666d0a>] start_secondary+0x19c/0x1a8
>
> The solution to that is use kasprintf in the CPU hotplug path
> that 'online's the CPU. That is, do it in in xen_hvm_cpu_notify,
> and remove the call to in xen_hvm_setup_cpu_clockevents.
>
> Unfortunatly the later is not a good idea as the bootup path
> does not use xen_hvm_cpu_notify so we would end up never allocating
> timer%d interrupt lines when booting. As such add the check for
> atomic() to continue.
This last is not reflected in the code.
Also, is it actually OK to move xen_setup_timer out of
xen_hvm_setup_cpu_clockevents?
xen_setup_cpu_clockevents registers xen_clock_events as clocksource and
xen_clock_events is setup by xen_setup_timer so we need to make sure
that the call order remains the same.
> CC: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
> arch/x86/xen/enlighten.c | 5 ++++-
> arch/x86/xen/time.c | 6 +++++-
> 2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 47d3243..ddbd54a 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1641,8 +1641,11 @@ static int __cpuinit xen_hvm_cpu_notify(struct notifier_block *self,
> switch (action) {
> case CPU_UP_PREPARE:
> xen_vcpu_setup(cpu);
> - if (xen_have_vector_callback)
> + if (xen_have_vector_callback) {
> xen_init_lock_cpu(cpu);
> + if (xen_feature(XENFEAT_hvm_safe_pvclock))
> + xen_setup_timer(cpu);
> + }
> break;
> default:
> break;
> diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
> index 0296a95..054cc01 100644
> --- a/arch/x86/xen/time.c
> +++ b/arch/x86/xen/time.c
> @@ -497,7 +497,11 @@ static void xen_hvm_setup_cpu_clockevents(void)
> {
> int cpu = smp_processor_id();
> xen_setup_runstate_info(cpu);
> - xen_setup_timer(cpu);
> + /*
> + * xen_setup_timer(cpu) - snprintf is bad in atomic context. Hence
> + * doing it xen_hvm_cpu_notify (which gets called by smp_init during
> + * early bootup and also during CPU hotplug events).
> + */
> xen_setup_cpu_clockevents();
> }
>
> --
> 1.8.1.4
>
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html