The patch titled
Subject: lazy tlb: introduce lazy tlb mm refcount helper functions
has been added to the -mm mm-unstable branch. Its filename is
lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Nicholas Piggin <npiggin@xxxxxxxxx>
Subject: lazy tlb: introduce lazy tlb mm refcount helper functions
Date: Fri, 3 Feb 2023 17:18:34 +1000
Add explicit _lazy_tlb annotated functions for lazy tlb mm refcounting.
This makes the lazy tlb mm references more obvious, and allows the
refcounting scheme to be modified in later changes. There is no
functional change with this patch.
Link: https://lkml.kernel.org/r/20230203071837.1136453-3-npiggin@xxxxxxxxx
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Acked-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Nadav Amit <nadav.amit@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
diff --git a/arch/arm/mach-rpc/ecard.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions b/arch/arm/mach-rpc/ecard.c
--- a/arch/arm/mach-rpc/ecard.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions
+++ b/arch/arm/mach-rpc/ecard.c
@@ -253,7 +253,7 @@ static int ecard_init_mm(void)
current->mm = mm;
current->active_mm = mm;
activate_mm(active_mm, mm);
- mmdrop(active_mm);
+ mmdrop_lazy_tlb(active_mm);
ecard_init_pgtables(mm);
return 0;
}
diff --git a/arch/powerpc/kernel/smp.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions b/arch/powerpc/kernel/smp.c
--- a/arch/powerpc/kernel/smp.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions
+++ b/arch/powerpc/kernel/smp.c
@@ -1611,7 +1611,7 @@ void start_secondary(void *unused)
if (IS_ENABLED(CONFIG_PPC32))
setup_kup();
- mmgrab(&init_mm);
+ mmgrab_lazy_tlb(&init_mm);
current->active_mm = &init_mm;
smp_store_cpu_info(cpu);
diff --git a/arch/powerpc/mm/book3s64/radix_tlb.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions b/arch/powerpc/mm/book3s64/radix_tlb.c
--- a/arch/powerpc/mm/book3s64/radix_tlb.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions
+++ b/arch/powerpc/mm/book3s64/radix_tlb.c
@@ -797,10 +797,10 @@ void exit_lazy_flush_tlb(struct mm_struct *mm, bool always_flush)
if (current->active_mm == mm) {
WARN_ON_ONCE(current->mm != NULL);
/* Is a kernel thread and is using mm as the lazy tlb */
- mmgrab(&init_mm);
+ mmgrab_lazy_tlb(&init_mm);
current->active_mm = &init_mm;
switch_mm_irqs_off(mm, &init_mm, current);
- mmdrop(mm);
+ mmdrop_lazy_tlb(mm);
}
/*
diff --git a/fs/exec.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions b/fs/exec.c
--- a/fs/exec.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions
+++ b/fs/exec.c
@@ -1034,7 +1034,7 @@ static int exec_mmap(struct mm_struct *mm)
mmput(old_mm);
return 0;
}
- mmdrop(active_mm);
+ mmdrop_lazy_tlb(active_mm);
return 0;
}
diff --git a/include/linux/sched/mm.h~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions b/include/linux/sched/mm.h
--- a/include/linux/sched/mm.h~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions
+++ b/include/linux/sched/mm.h
@@ -79,6 +79,22 @@ static inline void mmdrop_sched(struct mm_struct *mm)
}
#endif
+/* Helpers for lazy TLB mm refcounting */
+static inline void mmgrab_lazy_tlb(struct mm_struct *mm)
+{
+ mmgrab(mm);
+}
+
+static inline void mmdrop_lazy_tlb(struct mm_struct *mm)
+{
+ mmdrop(mm);
+}
+
+static inline void mmdrop_lazy_tlb_sched(struct mm_struct *mm)
+{
+ mmdrop_sched(mm);
+}
+
/**
* mmget() - Pin the address space associated with a &struct mm_struct.
* @mm: The address space to pin.
diff --git a/kernel/cpu.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions b/kernel/cpu.c
--- a/kernel/cpu.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions
+++ b/kernel/cpu.c
@@ -623,7 +623,7 @@ static int finish_cpu(unsigned int cpu)
*/
if (mm != &init_mm)
idle->active_mm = &init_mm;
- mmdrop(mm);
+ mmdrop_lazy_tlb(mm);
return 0;
}
diff --git a/kernel/exit.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions b/kernel/exit.c
--- a/kernel/exit.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions
+++ b/kernel/exit.c
@@ -537,7 +537,7 @@ static void exit_mm(void)
return;
sync_mm_rss(mm);
mmap_read_lock(mm);
- mmgrab(mm);
+ mmgrab_lazy_tlb(mm);
BUG_ON(mm != current->active_mm);
/* more a memory barrier than a real lock */
task_lock(current);
diff --git a/kernel/kthread.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions b/kernel/kthread.c
--- a/kernel/kthread.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions
+++ b/kernel/kthread.c
@@ -1415,6 +1415,11 @@ void kthread_use_mm(struct mm_struct *mm)
WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
WARN_ON_ONCE(tsk->mm);
+ /*
+ * It is possible for mm to be the same as tsk->active_mm, but
+ * we must still mmgrab(mm) and mmdrop_lazy_tlb(active_mm),
+ * because these references are not equivalent.
+ */
mmgrab(mm);
task_lock(tsk);
@@ -1438,9 +1443,9 @@ void kthread_use_mm(struct mm_struct *mm)
* memory barrier after storing to tsk->mm, before accessing
* user-space memory. A full memory barrier for membarrier
* {PRIVATE,GLOBAL}_EXPEDITED is implicitly provided by
- * mmdrop().
+ * mmdrop_lazy_tlb().
*/
- mmdrop(active_mm);
+ mmdrop_lazy_tlb(active_mm);
}
EXPORT_SYMBOL_GPL(kthread_use_mm);
@@ -1468,10 +1473,13 @@ void kthread_unuse_mm(struct mm_struct *mm)
local_irq_disable();
tsk->mm = NULL;
membarrier_update_current_mm(NULL);
+ mmgrab_lazy_tlb(mm);
/* active_mm is still 'mm' */
enter_lazy_tlb(mm, tsk);
local_irq_enable();
task_unlock(tsk);
+
+ mmdrop(mm);
}
EXPORT_SYMBOL_GPL(kthread_unuse_mm);
diff --git a/kernel/sched/core.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions b/kernel/sched/core.c
--- a/kernel/sched/core.c~lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions
+++ b/kernel/sched/core.c
@@ -5200,13 +5200,14 @@ static struct rq *finish_task_switch(struct task_struct *prev)
* rq->curr, before returning to userspace, so provide them here:
*
* - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
- * provided by mmdrop(),
+ * provided by mmdrop_lazy_tlb(),
* - a sync_core for SYNC_CORE.
*/
if (mm) {
membarrier_mm_sync_core_before_usermode(mm);
- mmdrop_sched(mm);
+ mmdrop_lazy_tlb_sched(mm);
}
+
if (unlikely(prev_state == TASK_DEAD)) {
if (prev->sched_class->task_dead)
prev->sched_class->task_dead(prev);
@@ -5263,9 +5264,9 @@ context_switch(struct rq *rq, struct task_struct *prev,
/*
* kernel -> kernel lazy + transfer active
- * user -> kernel lazy + mmgrab() active
+ * user -> kernel lazy + mmgrab_lazy_tlb() active
*
- * kernel -> user switch + mmdrop() active
+ * kernel -> user switch + mmdrop_lazy_tlb() active
* user -> user switch
*/
if (!next->mm) { // to kernel
@@ -5273,7 +5274,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
next->active_mm = prev->active_mm;
if (prev->mm) // from user
- mmgrab(prev->active_mm);
+ mmgrab_lazy_tlb(prev->active_mm);
else
prev->active_mm = NULL;
} else { // to user
@@ -5290,7 +5291,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
lru_gen_use_mm(next->mm);
if (!prev->mm) { // from kernel
- /* will mmdrop() in finish_task_switch(). */
+ /* will mmdrop_lazy_tlb() in finish_task_switch(). */
rq->prev_mm = prev->active_mm;
prev->active_mm = NULL;
}
@@ -9932,7 +9933,7 @@ void __init sched_init(void)
/*
* The boot idle thread does lazy MMU switching as well:
*/
- mmgrab(&init_mm);
+ mmgrab_lazy_tlb(&init_mm);
enter_lazy_tlb(&init_mm, current);
/*
_
Patches currently in -mm which might be from npiggin@xxxxxxxxx are
kthread-simplify-kthread_use_mm-refcounting.patch
lazy-tlb-introduce-lazy-tlb-mm-refcount-helper-functions.patch
lazy-tlb-allow-lazy-tlb-mm-refcounting-to-be-configurable.patch
lazy-tlb-shoot-lazies-non-refcounting-lazy-tlb-mm-reference-handling-scheme.patch
powerpc-64s-enable-mmu_lazy_tlb_shootdown.patch
