Hi,
This patch adds an annotations to clear_tasks_mm_cpumask(),
the function registers a warning of context imbalance when built with Sparse tool.
The adds fix the warning.
I also tested it and I think it is working fine.
I will appreciate any comment if possible.
Jules Irenge (1):
cpu: Add annotation inside clear_tasks_mm_cpumask()
kernel/cpu.c | 1 +
1 file changed, 1 insertion(+)
--
2.24.1
Sparse reports a warning
warning: context imbalance in clear_tasks_mm_cpumask() - different lock contexts for basic block
The root cause is the missing annotation inside clear_tasks_mm_cpumask()
Add the missing __acquire(&t->alloc_lock) annotation.
Signed-off-by: Jules Irenge <[email protected]>
---
kernel/cpu.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 9c706af713fb..d8c452a8dd09 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -834,6 +834,7 @@ void clear_tasks_mm_cpumask(int cpu)
t = find_lock_task_mm(p);
if (!t)
continue;
+ __acquire(&t->alloc_lock);
cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
task_unlock(t);
}
--
2.24.1
On Wed, Apr 15, 2020 at 07:49:37PM +0100, Jules Irenge wrote:
> Sparse reports a warning
>
> warning: context imbalance in clear_tasks_mm_cpumask() - different lock contexts for basic block
Does this sparse crap actually ever catch a real problem, or does it
only result in horrible code like this?
> The root cause is the missing annotation inside clear_tasks_mm_cpumask()
>
> Add the missing __acquire(&t->alloc_lock) annotation.
That's just wrong; the actual cause is find_lock_task_mm() not being
annotated, and the reason for that is because __cond_lock() is a
horrible piece of crap.
Barring any evidence that these annotations actually help anybody, can't
we just remove it all instead of making an ever bigger mess of things?
> Signed-off-by: Jules Irenge <[email protected]>
> ---
> kernel/cpu.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 9c706af713fb..d8c452a8dd09 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -834,6 +834,7 @@ void clear_tasks_mm_cpumask(int cpu)
> t = find_lock_task_mm(p);
> if (!t)
> continue;
> + __acquire(&t->alloc_lock);
> cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
> task_unlock(t);
> }
> --
> 2.24.1
>