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SubjectRe: scheduling while atomic in z3fold
On 2020-11-29 12:41:14 [+0100], Mike Galbraith wrote:
> On Sun, 2020-11-29 at 12:29 +0100, Oleksandr Natalenko wrote:
> >
> > Ummm so do compressors explode under non-rt kernel in your tests as
> > well, or it is just -rt that triggers this?
>
> I only tested a non-rt kernel with z3fold, which worked just fine.

I tried this and it did not not explode yet. Mike, can you please
confirm?

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 18feaa0bc5377..0bf70f624a4bd 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -642,14 +642,17 @@ static inline void add_to_unbuddied(struct z3fold_pool *pool,
{
if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
zhdr->middle_chunks == 0) {
- struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
-
+ struct list_head *unbuddied;
int freechunks = num_free_chunks(zhdr);
+
+ migrate_disable();
+ unbuddied = this_cpu_ptr(pool->unbuddied);
+
spin_lock(&pool->lock);
list_add(&zhdr->buddy, &unbuddied[freechunks]);
spin_unlock(&pool->lock);
zhdr->cpu = smp_processor_id();
- put_cpu_ptr(pool->unbuddied);
+ migrate_enable();
}
}

@@ -887,7 +890,8 @@ static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,

lookup:
/* First, try to find an unbuddied z3fold page. */
- unbuddied = get_cpu_ptr(pool->unbuddied);
+ migrate_disable();
+ unbuddied = this_cpu_ptr(pool->unbuddied);
for_each_unbuddied_list(i, chunks) {
struct list_head *l = &unbuddied[i];

@@ -905,7 +909,7 @@ static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
!z3fold_page_trylock(zhdr)) {
spin_unlock(&pool->lock);
zhdr = NULL;
- put_cpu_ptr(pool->unbuddied);
+ migrate_enable();
if (can_sleep)
cond_resched();
goto lookup;
@@ -919,7 +923,7 @@ static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
test_bit(PAGE_CLAIMED, &page->private)) {
z3fold_page_unlock(zhdr);
zhdr = NULL;
- put_cpu_ptr(pool->unbuddied);
+ migrate_enable();
if (can_sleep)
cond_resched();
goto lookup;
@@ -934,7 +938,7 @@ static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
kref_get(&zhdr->refcount);
break;
}
- put_cpu_ptr(pool->unbuddied);
+ migrate_enable();

if (!zhdr) {
int cpu;
diff --git a/mm/zswap.c b/mm/zswap.c
index 78a20f7b00f2c..b24f761b9241c 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -394,7 +394,9 @@ struct zswap_comp {
u8 *dstmem;
};

-static DEFINE_PER_CPU(struct zswap_comp, zswap_comp);
+static DEFINE_PER_CPU(struct zswap_comp, zswap_comp) = {
+ .lock = INIT_LOCAL_LOCK(lock),
+};

static int zswap_dstmem_prepare(unsigned int cpu)
{
> -Mike

Sebastian

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