lru_gen_add_mm() has been added within an IRQ-off region in the commit
mentioned below. The other invocations of lru_gen_add_mm() are not within
an IRQ-off region.
The invocation within IRQ-off region is problematic on PREEMPT_RT
because the function is using a spin_lock_t which must not be used
within IRQ-disabled regions.
The other invocations of lru_gen_add_mm() occur while task_struct::alloc_lock
is acquired.
Move lru_gen_add_mm() after interrupts are enabled and before
task_unlock().
Fixes: bd74fdaea1460 ("mm: multi-gen LRU: support page table walks")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
fs/exec.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1012,7 +1012,6 @@ static int exec_mmap(struct mm_struct *m
active_mm = tsk->active_mm;
tsk->active_mm = mm;
tsk->mm = mm;
- lru_gen_add_mm(mm);
/*
* This prevents preemption while active_mm is being loaded and
* it and mm are being updated, which could cause problems for
@@ -1025,6 +1024,7 @@ static int exec_mmap(struct mm_struct *m
activate_mm(active_mm, mm);
if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
local_irq_enable();
+ lru_gen_add_mm(mm);
task_unlock(tsk);
lru_gen_use_mm(mm);
if (old_mm) {
