On 03.11.25 19:29, Kevin Brodsky wrote:
On 03/11/2025 16:15, David Hildenbrand (Red Hat) wrote:
On 29.10.25 11:09, Kevin Brodsky wrote:
[...]
@@ -437,7 +436,7 @@ static void xen_end_context_switch(struct
task_struct *next)
xen_mc_flush();
leave_lazy(XEN_LAZY_CPU);
- if (test_and_clear_ti_thread_flag(task_thread_info(next),
TIF_LAZY_MMU_UPDATES))
+ if (next->lazy_mmu_state.active)
This is nasty. If in_lazy_mmu_mode() is not sufficient, we will want
to have a separate helper that makes it clear what the difference
between both variants is.
in_lazy_mmu_mode() operates on current, but here we're operating on a
different task. The difference is more fundamental than just passing a
task_struct * or not: in_lazy_mmu_mode() is about whether we're
currently in lazy MMU mode, i.e. not paused and not in interrupt
context. A task that isn't scheduled is never in lazy MMU mode -
lazy_mmu_state.active is just the saved state to be restored when
scheduled again.
My point here is that we could have a helper for this use-case, but it
should not be used in other situations (at least not on current). Maybe
__task_lazy_mmu_active(task)? I do wonder if accessing lazy_mmu_state
directly isn't expressing the intention well enough though (checking the
saved state).
Likely there should be a
/**
* task_lazy_mmu_active - test whether the lazy-mmu mode is active for a
* task
* @task: ...
*
* The lazy-mmu mode is active if a task has lazy-mmu mode enabled and
* currently not paused.
*/
static inline bool task_lazy_mmu_active(struct task_struct *task)
{
return task->lazy_mmu_state.active;
}
/**
* in_lazy_mmu_mode() - test whether current is in lazy-mmu mode
*
* Test whether the current task is in lazy-mmu mode: whether the
* interrupts are enabled and the lazy-mmu mode is active for the
* current task.
*/
static inline bool in_lazy_mmu_mode(void)
{
+ if (in_interrupt())
+ return false;
+
return task_lazy_mmu_active(current);
}
Something like that. Maybe we can find better terminology.
--
Cheers
David
