From 405efc5980f2590a9520dc66cfe295456b8c9818 Mon Sep 17 00:00:00 2001 From: "Christopher M. Riedl" Date: Mon, 12 Aug 2019 22:13:14 -0500 Subject: [PATCH] powerpc/spinlocks: Fix oops in __spin_yield() on bare metal Booting w/ppc64le_defconfig + CONFIG_PREEMPT on bare metal results in the oops below due to calling into __spin_yield() when not running in an SPLPAR, which means lppaca pointers are NULL. We fixed a similar case previously in commit a6201da34ff9 ("powerpc: Fix oops due to bad access of lppaca on bare metal"), by adding SPLPAR checks in lppaca_shared_proc(). However when PREEMPT is enabled we can call __spin_yield() directly from arch_spin_yield(). To fix it add spin_yield() and rw_yield() which check that shared-processor LPAR is enabled before calling the SPLPAR-only implementation of each. BUG: Kernel NULL pointer dereference at 0x00000100 Faulting instruction address: 0xc000000000097f88 Oops: Kernel access of bad area, sig: 7 [#1] LE PAGE_SIZE=64K MMU=Radix MMU=Hash PREEMPT SMP NR_CPUS=2048 NUMA PowerNV Modules linked in: CPU: 0 PID: 2 Comm: kthreadd Not tainted 5.2.0-rc6-00491-g249155c20f9b #28 NIP: c000000000097f88 LR: c000000000c07a88 CTR: c00000000015ca10 REGS: c0000000727079f0 TRAP: 0300 Not tainted (5.2.0-rc6-00491-g249155c20f9b) MSR: 9000000002009033 CR: 84000424 XER: 20040000 CFAR: c000000000c07a84 DAR: 0000000000000100 DSISR: 00080000 IRQMASK: 1 GPR00: c000000000c07a88 c000000072707c80 c000000001546300 c00000007be38a80 GPR04: c0000000726f0c00 0000000000000002 c00000007279c980 0000000000000100 GPR08: c000000001581b78 0000000080000001 0000000000000008 c00000007279c9b0 GPR12: 0000000000000000 c000000001730000 c000000000142558 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 GPR24: c00000007be38a80 c000000000c002f4 0000000000000000 0000000000000000 GPR28: c000000072221a00 c0000000726c2600 c00000007be38a80 c00000007be38a80 NIP [c000000000097f88] __spin_yield+0x48/0xa0 LR [c000000000c07a88] __raw_spin_lock+0xb8/0xc0 Call Trace: [c000000072707c80] [c000000072221a00] 0xc000000072221a00 (unreliable) [c000000072707cb0] [c000000000bffb0c] __schedule+0xbc/0x850 [c000000072707d70] [c000000000c002f4] schedule+0x54/0x130 [c000000072707da0] [c0000000001427dc] kthreadd+0x28c/0x2b0 [c000000072707e20] [c00000000000c1cc] ret_from_kernel_thread+0x5c/0x70 Instruction dump: 4d9e0020 552a043e 210a07ff 79080fe0 0b080000 3d020004 3908b878 794a1f24 e8e80000 7ce7502a e8e70000 38e70100 <7ca03c2c> 70a70001 78a50020 4d820020 ---[ end trace 474d6b2b8fc5cb7e ]--- Fixes: 499dcd41378e ("powerpc/64s: Allocate LPPACAs individually") Signed-off-by: Christopher M. Riedl [mpe: Reword change log a bit] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20190813031314.1828-4-cmr@informatik.wtf --- arch/powerpc/include/asm/spinlock.h | 36 ++++++++++++++++++++--------- 1 file changed, 25 insertions(+), 11 deletions(-) diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h index 0d04d468f660..e9a960e28f3c 100644 --- a/arch/powerpc/include/asm/spinlock.h +++ b/arch/powerpc/include/asm/spinlock.h @@ -103,11 +103,9 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock) /* We only yield to the hypervisor if we are in shared processor mode */ void splpar_spin_yield(arch_spinlock_t *lock); void splpar_rw_yield(arch_rwlock_t *lock); -#define __spin_yield(x) splpar_spin_yield(x) -#define __rw_yield(x) splpar_rw_yield(x) #else /* SPLPAR */ -#define __spin_yield(x) barrier() -#define __rw_yield(x) barrier() +static inline void splpar_spin_yield(arch_spinlock_t *lock) {}; +static inline void splpar_rw_yield(arch_rwlock_t *lock) {}; #endif static inline bool is_shared_processor(void) @@ -124,6 +122,22 @@ static inline bool is_shared_processor(void) #endif } +static inline void spin_yield(arch_spinlock_t *lock) +{ + if (is_shared_processor()) + splpar_spin_yield(lock); + else + barrier(); +} + +static inline void rw_yield(arch_rwlock_t *lock) +{ + if (is_shared_processor()) + splpar_rw_yield(lock); + else + barrier(); +} + static inline void arch_spin_lock(arch_spinlock_t *lock) { while (1) { @@ -132,7 +146,7 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) do { HMT_low(); if (is_shared_processor()) - __spin_yield(lock); + splpar_spin_yield(lock); } while (unlikely(lock->slock != 0)); HMT_medium(); } @@ -151,7 +165,7 @@ void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags) do { HMT_low(); if (is_shared_processor()) - __spin_yield(lock); + splpar_spin_yield(lock); } while (unlikely(lock->slock != 0)); HMT_medium(); local_irq_restore(flags_dis); @@ -241,7 +255,7 @@ static inline void arch_read_lock(arch_rwlock_t *rw) do { HMT_low(); if (is_shared_processor()) - __rw_yield(rw); + splpar_rw_yield(rw); } while (unlikely(rw->lock < 0)); HMT_medium(); } @@ -255,7 +269,7 @@ static inline void arch_write_lock(arch_rwlock_t *rw) do { HMT_low(); if (is_shared_processor()) - __rw_yield(rw); + splpar_rw_yield(rw); } while (unlikely(rw->lock != 0)); HMT_medium(); } @@ -295,9 +309,9 @@ static inline void arch_write_unlock(arch_rwlock_t *rw) rw->lock = 0; } -#define arch_spin_relax(lock) __spin_yield(lock) -#define arch_read_relax(lock) __rw_yield(lock) -#define arch_write_relax(lock) __rw_yield(lock) +#define arch_spin_relax(lock) spin_yield(lock) +#define arch_read_relax(lock) rw_yield(lock) +#define arch_write_relax(lock) rw_yield(lock) /* See include/linux/spinlock.h */ #define smp_mb__after_spinlock() smp_mb()