On Fri, 2018-05-18 at 11:19 +0200, Sebastian Andrzej Siewior wrote:
>
> - Add a locallock during saving/restoring of SIMD registers on ARM64.
> On RT we are preemptible there so extra protection is required.
From: Mike Galbraith <efault@xxxxxx>
[ 2.106296] BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:974
[ 2.106361] in_atomic(): 1, irqs_disabled(): 0, pid: 1, name: swapper/0
[ 2.106416] Preemption disabled at:
[ 2.106556] [<ffff0b5ce3b2cf58>] efi_virtmap_load+0x18/0x38
[ 2.106761] CPU: 7 PID: 1 Comm: swapper/0 Not tainted 4.16.17-rt7-rt #4
[ 2.106775] Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
[ 2.106902] Call trace:
[ 2.106927] dump_backtrace+0x0/0x1c8
[ 2.106948] show_stack+0x24/0x30
[ 2.106957] dump_stack+0xac/0xe8
[ 2.106966] ___might_sleep+0x124/0x188
[ 2.106973] rt_spin_lock+0x40/0x88
[ 2.106993] kernel_neon_begin+0x90/0x170
[ 2.107008] __efi_fpsimd_begin+0x68/0x1a0
[ 2.107019] virt_efi_get_next_variable+0x48/0xc8
[ 2.107026] efivar_init+0xb0/0x380
[ 2.107039] efisubsys_init+0xd4/0x26c
[ 2.107045] do_one_initcall+0x58/0x168
[ 2.107053] kernel_init_freeable+0x1e0/0x284
[ 2.107062] kernel_init+0x18/0x118
[ 2.107071] ret_from_fork+0x10/0x18
("arm64: fpsimd: use a local_lock() in addition to local_bh_disable()")
added a local_lock(), which efi_virtmap_load()/efi_virtmap_unload() can
encase in a preempt disabled section during boot. Make that section
preemptible via another local_lock().
Signed-off-by: Mike Galbraith <efault@xxxxxx>
---
arch/arm64/kernel/fpsimd.c | 3 ++-
drivers/firmware/efi/arm-runtime.c | 7 +++++--
2 files changed, 7 insertions(+), 3 deletions(-)
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1201,7 +1201,8 @@ void __efi_fpsimd_begin(void)
if (!system_supports_fpsimd())
return;
- WARN_ON(preemptible());
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT_BASE))
+ WARN_ON(preemptible());
if (may_use_simd()) {
kernel_neon_begin();
--- a/drivers/firmware/efi/arm-runtime.c
+++ b/drivers/firmware/efi/arm-runtime.c
@@ -22,6 +22,7 @@
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
+#include <linux/locallock.h>
#include <asm/cacheflush.h>
#include <asm/efi.h>
@@ -159,16 +160,18 @@ static int __init arm_enable_runtime_ser
}
early_initcall(arm_enable_runtime_services);
+static DEFINE_LOCAL_IRQ_LOCK(efi_virtmap_lock);
+
void efi_virtmap_load(void)
{
- preempt_disable();
+ local_lock(efi_virtmap_lock);
efi_set_pgd(&efi_mm);
}
void efi_virtmap_unload(void)
{
efi_set_pgd(current->active_mm);
- preempt_enable();
+ local_unlock(efi_virtmap_lock);
}
--
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