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Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0019-x86-efi-drop-task_lock-from-efi_switch_mm.patch | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/debian/patches-rt/0019-x86-efi-drop-task_lock-from-efi_switch_mm.patch b/debian/patches-rt/0019-x86-efi-drop-task_lock-from-efi_switch_mm.patch new file mode 100644 index 000000000..cc5aa4db1 --- /dev/null +++ b/debian/patches-rt/0019-x86-efi-drop-task_lock-from-efi_switch_mm.patch @@ -0,0 +1,55 @@ +From dc7eee776061da65e8343c30c068e3862a192bef Mon Sep 17 00:00:00 2001 +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Tue, 24 Jul 2018 14:48:55 +0200 +Subject: [PATCH 019/347] x86/efi: drop task_lock() from efi_switch_mm() +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +efi_switch_mm() is a wrapper around switch_mm() which saves current's +->active_mm, sets the requests mm as ->active_mm and invokes +switch_mm(). +I don't think that task_lock() is required during that procedure. It +protects ->mm which isn't changed here. + +It needs to be mentioned that during the whole procedure (switch to +EFI's mm and back) the preemption needs to be disabled. A context switch +at this point would reset the cr3 value based on current->mm. Also, this +function may not be invoked at the same time on a different CPU because +it would overwrite the efi_scratch.prev_mm information. + +Remove task_lock() and also update the comment to reflect it. + +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + arch/x86/platform/efi/efi_64.c | 10 ++++------ + 1 file changed, 4 insertions(+), 6 deletions(-) + +diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c +index 77d05b56089a..cd7e4bfb43cf 100644 +--- a/arch/x86/platform/efi/efi_64.c ++++ b/arch/x86/platform/efi/efi_64.c +@@ -619,18 +619,16 @@ void __init efi_dump_pagetable(void) + + /* + * Makes the calling thread switch to/from efi_mm context. Can be used +- * for SetVirtualAddressMap() i.e. current->active_mm == init_mm as well +- * as during efi runtime calls i.e current->active_mm == current_mm. +- * We are not mm_dropping()/mm_grabbing() any mm, because we are not +- * losing/creating any references. ++ * in a kernel thread and user context. Preemption needs to remain disabled ++ * while the EFI-mm is borrowed. mmgrab()/mmdrop() is not used because the mm ++ * can not change under us. ++ * It should be ensured that there are no concurent calls to this function. + */ + void efi_switch_mm(struct mm_struct *mm) + { +- task_lock(current); + efi_scratch.prev_mm = current->active_mm; + current->active_mm = mm; + switch_mm(efi_scratch.prev_mm, mm, NULL); +- task_unlock(current); + } + + #ifdef CONFIG_EFI_MIXED +-- +2.36.1 + |