mirror of
https://github.com/FEX-Emu/linux.git
synced 2025-01-21 09:23:51 +00:00
powerpc/rtas: Fix a potential race between CPU-Offline & Migration
Live Partition Migrations require all the present CPUs to execute the H_JOIN call, and hence rtas_ibm_suspend_me() onlines any offline CPUs before initiating the migration for this purpose. The commit 85a88cabad57 ("powerpc/pseries: Disable CPU hotplug across migrations") disables any CPU-hotplug operations once all the offline CPUs are brought online to prevent any further state change. Once the CPU-Hotplug operation is disabled, the code assumes that all the CPUs are online. However, there is a minor window in rtas_ibm_suspend_me() between onlining the offline CPUs and disabling CPU-Hotplug when a concurrent CPU-offline operations initiated by the userspace can succeed thereby nullifying the the aformentioned assumption. In this unlikely case these offlined CPUs will not call H_JOIN, resulting in a system hang. Fix this by verifying that all the present CPUs are actually online after CPU-Hotplug has been disabled, failing which we restore the state of the offline CPUs in rtas_ibm_suspend_me() and return an -EBUSY. Cc: Nathan Fontenot <nfont@linux.vnet.ibm.com> Cc: Tyrel Datwyler <tyreld@linux.vnet.ibm.com> Suggested-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> Reviewed-by: Nathan Fontenot <nfont@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
parent
500fe5f550
commit
dfd718a2ed
@ -983,6 +983,14 @@ int rtas_ibm_suspend_me(u64 handle)
|
||||
|
||||
cpu_hotplug_disable();
|
||||
|
||||
/* Check if we raced with a CPU-Offline Operation */
|
||||
if (unlikely(!cpumask_equal(cpu_present_mask, cpu_online_mask))) {
|
||||
pr_err("%s: Raced against a concurrent CPU-Offline\n",
|
||||
__func__);
|
||||
atomic_set(&data.error, -EBUSY);
|
||||
goto out_hotplug_enable;
|
||||
}
|
||||
|
||||
/* Call function on all CPUs. One of us will make the
|
||||
* rtas call
|
||||
*/
|
||||
@ -994,6 +1002,7 @@ int rtas_ibm_suspend_me(u64 handle)
|
||||
if (atomic_read(&data.error) != 0)
|
||||
printk(KERN_ERR "Error doing global join\n");
|
||||
|
||||
out_hotplug_enable:
|
||||
cpu_hotplug_enable();
|
||||
|
||||
/* Take down CPUs not online prior to suspend */
|
||||
|
Loading…
x
Reference in New Issue
Block a user