[PATCH v4 21/35] mm, slub: call deactivate_slab() without disabling irqs
STALE1865d
From: Vlastimil Babka <hidden>
Date: 2021-08-05 15:24:50
Also in:
lkml
Subsystem:
memory management, slab allocator, the rest · Maintainers:
Andrew Morton, Vlastimil Babka, Harry Yoo, Linus Torvalds
Revision v4 of 4 in this series.
Revisions (4)
- v3 [diff vs current]
- v4 current
- v5 [diff vs current]
- v6 [diff vs current]
The function is now safe to be called with irqs enabled, so move the calls outside of irq disabled sections. When called from ___slab_alloc() -> flush_slab() we have irqs disabled, so to reenable them before deactivate_slab() we need to open-code flush_slab() in ___slab_alloc() and reenable irqs after modifying the kmem_cache_cpu fields. But that means a IRQ handler meanwhile might have assigned a new page to kmem_cache_cpu.page so we have to retry the whole check. The remaining callers of flush_slab() are the IPI handler which has disabled irqs anyway, and slub_cpu_dead() which will be dealt with in the following patch. Signed-off-by: Vlastimil Babka <redacted> --- mm/slub.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 27c98f4fb3f5..8de4ead2dbf3 100644
--- a/mm/slub.c
+++ b/mm/slub.c@@ -2749,8 +2749,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, freelist = c->freelist; c->page = NULL; c->freelist = NULL; - deactivate_slab(s, page, freelist); local_irq_restore(flags); + deactivate_slab(s, page, freelist); new_slab:
@@ -2818,18 +2818,32 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, */ goto return_single; +retry_load_page: + local_irq_save(flags); - if (unlikely(c->page)) - flush_slab(s, c); + if (unlikely(c->page)) { + void *flush_freelist = c->freelist; + struct page *flush_page = c->page; + + c->page = NULL; + c->freelist = NULL; + c->tid = next_tid(c->tid); + + local_irq_restore(flags); + + deactivate_slab(s, flush_page, flush_freelist); + + stat(s, CPUSLAB_FLUSH); + + goto retry_load_page; + } c->page = page; goto load_freelist; return_single: - local_irq_save(flags); deactivate_slab(s, page, get_freepointer(s, freelist)); - local_irq_restore(flags); return freelist; }
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2.32.0