Greetings,
$subject puts task_lock() in preempt and irq disabled sections for RT.
I have two solutions, neither optimal, one fugly. Better ideas welcome.
[ 0.468061] BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:974
[ 0.468062] in_atomic(): 1, irqs_disabled(): 0, pid: 1, name: swapper/0
[ 0.468062] 1 lock held by swapper/0/1:
[ 0.468063] #0: (&p->alloc_lock){+.+.}, at: [<ffffffffb906e604>] efi_switch_mm+0x24/0x50
[ 0.468067] Preemption disabled at:
[ 0.468070] [<ffffffffb960c987>] virt_efi_get_next_variable+0x47/0x190
[ 0.468072] CPU: 6 PID: 1 Comm: swapper/0 Not tainted 4.16.0.g557ca5a-rt19-tip-rt #68
[ 0.468072] Hardware name: MEDION MS-7848/MS-7848, BIOS M7848W08.20C 09/23/2013
[ 0.468073] Call Trace:
[ 0.468077] dump_stack+0x78/0xab
[ 0.468080] ___might_sleep+0x1f5/0x250
[ 0.468083] rt_spin_lock+0x49/0x60
[ 0.468085] ? efi_switch_mm+0x24/0x50
[ 0.468086] efi_switch_mm+0x24/0x50
[ 0.468088] virt_efi_get_next_variable+0x187/0x190
[ 0.468090] efivar_init+0xea/0x350
[ 0.468093] ? efivar_ssdt_setup+0x3b/0x3b
[ 0.468096] ? _raw_spin_unlock_irqrestore+0x85/0xa0
[ 0.468097] ? preempt_count_sub+0x6a/0xe0
[ 0.468101] efisubsys_init+0xee/0x298
[ 0.468103] ? match_config_table+0x120/0x120
[ 0.468106] do_one_initcall+0x50/0x1a7
[ 0.468111] kernel_init_freeable+0x22b/0x2b3
[ 0.468112] ? set_debug_rodata+0x11/0x11
[ 0.468118] ? rest_init+0xd0/0xd0
[ 0.468119] kernel_init+0xa/0x110
[ 0.468120] ret_from_fork+0x3a/0x50
0. revert annoying commit for RT (nope).
1. tell assorted efi goop to go away, taking lock with it.
---
arch/x86/platform/efi/efi.c | 2 ++
1 file changed, 2 insertions(+)
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -493,6 +493,8 @@ void __init efi_init(void)
efi_phys.systab = (efi_system_table_t *)
(boot_params.efi_info.efi_systab |
((__u64)boot_params.efi_info.efi_systab_hi<<32));
+ if (IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+ set_bit(EFI_OLD_MEMMAP, &efi.flags);
#endif
if (efi_systab_init(efi_phys.systab))
2. move troublesome lock.
---
arch/x86/include/asm/efi.h | 8 ++++++++
arch/x86/platform/efi/efi_64.c | 20 ++++++++++++++++++--
2 files changed, 26 insertions(+), 2 deletions(-)
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -81,6 +81,10 @@ struct efi_scratch {
#define arch_efi_call_virt_setup() \
({ \
+ if (IS_ENABLED(CONFIG_PREEMPT_RT_FULL)) { \
+ if (!efi_enabled(EFI_OLD_MEMMAP)) \
+ spin_lock(¤t->alloc_lock); \
+ } \
efi_sync_low_kernel_mappings(); \
preempt_disable(); \
__kernel_fpu_begin(); \
@@ -101,6 +105,10 @@ struct efi_scratch {
firmware_restrict_branch_speculation_end(); \
__kernel_fpu_end(); \
preempt_enable(); \
+ if (IS_ENABLED(CONFIG_PREEMPT_RT_FULL)) { \
+ if (!efi_enabled(EFI_OLD_MEMMAP)) \
+ spin_unlock(¤t->alloc_lock); \
+ } \
})
extern void __iomem *__init efi_ioremap(unsigned long addr, unsigned long size,
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -83,7 +83,11 @@ pgd_t * __init efi_call_phys_prolog(void
int n_pgds, i, j;
if (!efi_enabled(EFI_OLD_MEMMAP)) {
+ if (IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+ task_lock(current);
efi_switch_mm(&efi_mm);
+ if (IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+ task_unlock(current);
return NULL;
}
@@ -156,7 +160,11 @@ void __init efi_call_phys_epilog(pgd_t *
pud_t *pud;
if (!efi_enabled(EFI_OLD_MEMMAP)) {
+ if (IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+ task_lock(current);
efi_switch_mm(efi_scratch.prev_mm);
+ if (IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+ task_unlock(current);
return;
}
@@ -626,11 +634,15 @@ void __init efi_dump_pagetable(void)
*/
void efi_switch_mm(struct mm_struct *mm)
{
- task_lock(current);
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+ task_lock(current);
+ else
+ lockdep_assert_held(¤t->alloc_lock);
efi_scratch.prev_mm = current->active_mm;
current->active_mm = mm;
switch_mm(efi_scratch.prev_mm, mm, NULL);
- task_unlock(current);
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+ task_unlock(current);
}
#ifdef CONFIG_EFI_MIXED
@@ -683,6 +695,8 @@ efi_status_t efi_thunk_set_virtual_addre
unsigned long flags;
u32 func;
+ if (IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+ task_lock(current);
efi_sync_low_kernel_mappings();
local_irq_save(flags);
@@ -694,6 +708,8 @@ efi_status_t efi_thunk_set_virtual_addre
efi_switch_mm(efi_scratch.prev_mm);
local_irq_restore(flags);
+ if (IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+ task_unlock(current);
return status;
}
--
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