The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From b9ee5e04fd77898208c51b1395fa0b5e8536f9b6 Mon Sep 17 00:00:00 2001
From: Christophe Leroy christophe.leroy@c-s.fr Date: Thu, 8 Aug 2019 12:48:26 +0000 Subject: [PATCH] powerpc/64e: Drop stale call to smp_processor_id() which hangs SMP startup
Commit ebb9d30a6a74 ("powerpc/mm: any thread in one core can be the first to setup TLB1") removed the need to know the cpu_id in early_init_this_mmu(), but the call to smp_processor_id() which was marked __maybe_used remained.
Since commit ed1cd6deb013 ("powerpc: Activate CONFIG_THREAD_INFO_IN_TASK") thread_info cannot be reached before MMU is properly set up.
Drop this stale call to smp_processor_id() which makes SMP hang when CONFIG_PREEMPT is set.
Fixes: ebb9d30a6a74 ("powerpc/mm: any thread in one core can be the first to setup TLB1") Fixes: ed1cd6deb013 ("powerpc: Activate CONFIG_THREAD_INFO_IN_TASK") Cc: stable@vger.kernel.org # v5.1+ Reported-by: Chris Packham Chris.Packham@alliedtelesis.co.nz Signed-off-by: Christophe Leroy christophe.leroy@c-s.fr Tested-by: Chris Packham chris.packham@alliedtelesis.co.nz Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/bef479514f4c08329fa649f67735df8918bc0976.156526824...
diff --git a/arch/powerpc/mm/nohash/tlb.c b/arch/powerpc/mm/nohash/tlb.c index d4acf6fa0596..bf60983a58c7 100644 --- a/arch/powerpc/mm/nohash/tlb.c +++ b/arch/powerpc/mm/nohash/tlb.c @@ -630,7 +630,6 @@ static void early_init_this_mmu(void) #ifdef CONFIG_PPC_FSL_BOOK3E if (mmu_has_feature(MMU_FTR_TYPE_FSL_E)) { unsigned int num_cams; - int __maybe_unused cpu = smp_processor_id(); bool map = true;
/* use a quarter of the TLBCAM for bolted linear map */