| Message ID | 1422483604-13203-1-git-send-email-kamal@canonical.com |
|---|---|
| State | New |
| Headers | show |
On Wed, 2015-01-28 at 14:20 -0800, Kamal Mostafa wrote: > This is a note to let you know that I have just added a patch titled > > powerpc: Secondary CPUs must set cpu_callin_map after setting active and online > > to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree > which can be found at: > > http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue > > This patch is scheduled to be released in version 3.13.11-ckt15. > > If you, or anyone else, feels it should not be added to this tree, please > reply to this email. Please drop this patch. It's been reverted upstream, by me. cheers
On Thu, 2015-01-29 at 11:35 +1100, Michael Ellerman wrote: > On Wed, 2015-01-28 at 14:20 -0800, Kamal Mostafa wrote: > > This is a note to let you know that I have just added a patch titled > > > > powerpc: Secondary CPUs must set cpu_callin_map after setting active and online > > > Please drop this patch. > > It's been reverted upstream, by me. Okay, dropped from 3.13-stable. Thanks Michael. -Kamal
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c index c1cf4a1..a2802c1 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -712,7 +712,6 @@ void start_secondary(void *unused) smp_store_cpu_info(cpu); set_dec(tb_ticks_per_jiffy); preempt_disable(); - cpu_callin_map[cpu] = 1; if (smp_ops->setup_cpu) smp_ops->setup_cpu(cpu); @@ -748,6 +747,14 @@ void start_secondary(void *unused) notify_cpu_starting(cpu); set_cpu_online(cpu, true); + /* + * CPU must be marked active and online before we signal back to the + * master, because the scheduler needs to see the cpu_online and + * cpu_active bits set. + */ + smp_wmb(); + cpu_callin_map[cpu] = 1; + local_irq_enable(); cpu_startup_entry(CPUHP_ONLINE);
This is a note to let you know that I have just added a patch titled powerpc: Secondary CPUs must set cpu_callin_map after setting active and online to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue This patch is scheduled to be released in version 3.13.11-ckt15. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.13.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From 9b59325c3e5ea9f9b926e475dd9ae9bf0ffa170f Mon Sep 17 00:00:00 2001 From: Anton Blanchard <anton@samba.org> Date: Tue, 9 Dec 2014 10:58:19 +1100 Subject: powerpc: Secondary CPUs must set cpu_callin_map after setting active and online commit 7c5c92ed56d932b2c19c3f8aea86369509407d33 upstream. I have a busy ppc64le KVM box where guests sometimes hit the infamous "kernel BUG at kernel/smpboot.c:134!" issue during boot: BUG_ON(td->cpu != smp_processor_id()); Basically a per CPU hotplug thread scheduled on the wrong CPU. The oops output confirms it: CPU: 0 Comm: watchdog/130 The problem is that we aren't ensuring the CPU active and online bits are set before allowing the master to continue on. The master unparks the secondary CPUs kthreads and the scheduler looks for a CPU to run on. It calls select_task_rq and realises the suggested CPU is not in the cpus_allowed mask. It then ends up in select_fallback_rq, and since the active and online bits aren't set we choose some other CPU to run on. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/powerpc/kernel/smp.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) -- 1.9.1