From: Nathan Lynch nathanl@linux.ibm.com
[ Upstream commit 9fb603050ffd94f8127df99c699cca2f575eb6a0 ]
The protocol for suspending or migrating an LPAR requires all present processor threads to enter H_JOIN. So if we have threads offline, we have to temporarily bring them up. This can race with administrator actions such as SMT state changes. As of dfd718a2ed1f ("powerpc/rtas: Fix a potential race between CPU-Offline & Migration"), rtas_ibm_suspend_me() accounts for this, but errors out with -EBUSY for what almost certainly is a transient condition in any reasonable scenario.
Callers of rtas_ibm_suspend_me() already retry when -EAGAIN is returned, and it is typical during a migration for that to happen repeatedly for several minutes polling the H_VASI_STATE hcall result before proceeding to the next stage.
So return -EAGAIN instead of -EBUSY when this race is encountered. Additionally: logging this event is still appropriate but use pr_info instead of pr_err; and remove use of unlikely() while here as this is not a hot path at all.
Fixes: dfd718a2ed1f ("powerpc/rtas: Fix a potential race between CPU-Offline & Migration") Signed-off-by: Nathan Lynch nathanl@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/kernel/rtas.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c index b824f4c69622..fff2eb22427d 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -980,10 +980,9 @@ 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); + if (!cpumask_equal(cpu_present_mask, cpu_online_mask)) { + pr_info("%s: Raced against a concurrent CPU-Offline\n", __func__); + atomic_set(&data.error, -EAGAIN); goto out_hotplug_enable; }