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SubjectRE: [PATCH v2] kasan: Fix sleeping function called from invalid context on RT kernel
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On Fri, 1 Apr 2022 21:46:49 +0800 Zqiang <qiang1.zhang@intel.com> wrote:

> When the kmem_cache_shrink() be called, the IPI was triggered, the
> ___cache_free() is called in IPI interrupt context, the local-lock or
> spin-lock will be acquired. on PREEMPT_RT kernel, these lock is
> replaced with sleepbale rt-spinlock, so the above problem is triggered.
> fix it by move the qlist_free_allfrom() the IPI interrupt context to
> the task context when PREEMPT_RT is enabled.
>
>This patch is rather ifdeffy so I propose the below cleanup. Please review and test?

Thanks, it looks clearer.

>Note that it incorporates the changes from your https://lkml.kernel.org/r/20220414025925.2423818-1-qiang1.zhang@intel.com
>
>btw, how are we supposed to test PREEMPT_RT builds? I had to patch arch/Kconfig.

The attachment is a config file and I test with linux-5.17.y-rt branch (https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git), I have been tested.

Thanks
Zqiang

>
--- a/mm/kasan/quarantine.c~kasan-fix-sleeping-function-called-from-invalid-context-on-rt-kernel-fix
+++ a/mm/kasan/quarantine.c
@@ -319,28 +319,37 @@ static void qlist_move_cache(struct qlis
}
}

-static void per_cpu_remove_cache(void *arg)
+#ifndef CONFIG_PREEMPT_RT
+static void __per_cpu_remove_cache(struct qlist_head *q, void *arg)
{
struct kmem_cache *cache = arg;
- struct qlist_head *q;
-#ifndef CONFIG_PREEMPT_RT
struct qlist_head to_free = QLIST_INIT; -#else
- unsigned long flags;
- struct cpu_shrink_qlist *sq;
-#endif
- q = this_cpu_ptr(&cpu_quarantine);
-#ifndef CONFIG_PREEMPT_RT
- if (READ_ONCE(q->offline))
- return;
+
qlist_move_cache(q, &to_free, cache);
qlist_free_all(&to_free, cache);
+}
#else
+static void __per_cpu_remove_cache(struct qlist_head *q, void *arg) {
+ struct kmem_cache *cache = arg;
+ unsigned long flags;
+ struct cpu_shrink_qlist *sq;
+
sq = this_cpu_ptr(&shrink_qlist);
raw_spin_lock_irqsave(&sq->lock, flags);
qlist_move_cache(q, &sq->qlist, cache);
raw_spin_unlock_irqrestore(&sq->lock, flags);
+}
#endif
+
+static void per_cpu_remove_cache(void *arg) {
+ struct qlist_head *q;
+
+ q = this_cpu_ptr(&cpu_quarantine);
+ if (READ_ONCE(q->offline))
+ return;
+ __per_cpu_remove_cache(q, arg);
}

/* Free all quarantined objects belonging to cache. */ @@ -348,10 +357,6 @@ void kasan_quarantine_remove_cache(struc
{
unsigned long flags, i;
struct qlist_head to_free = QLIST_INIT; -#ifdef CONFIG_PREEMPT_RT
- int cpu;
- struct cpu_shrink_qlist *sq;
-#endif

/*
* Must be careful to not miss any objects that are being moved from @@ -363,13 +368,18 @@ void kasan_quarantine_remove_cache(struc
on_each_cpu(per_cpu_remove_cache, cache, 1);

#ifdef CONFIG_PREEMPT_RT
- for_each_online_cpu(cpu) {
- sq = per_cpu_ptr(&shrink_qlist, cpu);
- raw_spin_lock_irqsave(&sq->lock, flags);
- qlist_move_cache(&sq->qlist, &to_free, cache);
- raw_spin_unlock_irqrestore(&sq->lock, flags);
+ {
+ int cpu;
+ struct cpu_shrink_qlist *sq;
+
+ for_each_online_cpu(cpu) {
+ sq = per_cpu_ptr(&shrink_qlist, cpu);
+ raw_spin_lock_irqsave(&sq->lock, flags);
+ qlist_move_cache(&sq->qlist, &to_free, cache);
+ raw_spin_unlock_irqrestore(&sq->lock, flags);
+ }
+ qlist_free_all(&to_free, cache);
}
- qlist_free_all(&to_free, cache);
#endif

raw_spin_lock_irqsave(&quarantine_lock, flags); _

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