+ mm-slub-make-slab_lock-disable-irqs-with-preempt_rt.patch added to -mm tree

+ mm-slub-make-slab_lock-disable-irqs-with-preempt_rt.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm, slub: make slab_lock() disable irqs with PREEMPT_RT
has been added to the -mm tree.  Its filename is
     mm-slub-make-slab_lock-disable-irqs-with-preempt_rt.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-slub-make-slab_lock-disable-irqs-with-preempt_rt.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-slub-make-slab_lock-disable-irqs-with-preempt_rt.patch

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------------------------------------------------------
From: Vlastimil Babka <vbabka@suse.cz>
Subject: mm, slub: make slab_lock() disable irqs with PREEMPT_RT

We need to disable irqs around slab_lock() (a bit spinlock) to make it
irq-safe.  The calls to slab_lock() are nested under spin_lock_irqsave()
which doesn't disable irqs on PREEMPT_RT, so add explicit disabling with
PREEMPT_RT.

We also distinguish cmpxchg_double_slab() where we do the disabling
explicitly and __cmpxchg_double_slab() for contexts with already disabled
irqs.  However these context are also typically spin_lock_irqsave() thus
insufficient on PREEMPT_RT.  Thus, change __cmpxchg_double_slab() to be
same as cmpxchg_double_slab() on PREEMPT_RT.

Link: https://lkml.kernel.org/r/20210805152000.12817-33-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/slub.c |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

--- a/mm/slub.c~mm-slub-make-slab_lock-disable-irqs-with-preempt_rt
+++ a/mm/slub.c
@@ -380,12 +380,12 @@ __slab_unlock(struct page *page, unsigne
 static __always_inline void
 slab_lock(struct page *page, unsigned long *flags)
 {
-	__slab_lock(page, flags, false);
+	__slab_lock(page, flags, IS_ENABLED(CONFIG_PREEMPT_RT));
 }
 
 static __always_inline void slab_unlock(struct page *page, unsigned long *flags)
 {
-	__slab_unlock(page, flags, false);
+	__slab_unlock(page, flags, IS_ENABLED(CONFIG_PREEMPT_RT));
 }
 
 static inline bool ___cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
@@ -429,14 +429,19 @@ static inline bool ___cmpxchg_double_sla
 	return false;
 }
 
-/* Interrupts must be disabled (for the fallback code to work right) */
+/*
+ * Interrupts must be disabled (for the fallback code to work right), typically
+ * by an _irqsave() lock variant. Except on PREEMPT_RT where locks are different
+ * so we disable interrupts explicitly here.
+ */
 static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
 		void *freelist_old, unsigned long counters_old,
 		void *freelist_new, unsigned long counters_new,
 		const char *n)
 {
 	return ___cmpxchg_double_slab(s, page, freelist_old, counters_old,
-				      freelist_new, counters_new, n, false);
+				      freelist_new, counters_new, n,
+				      IS_ENABLED(CONFIG_PREEMPT_RT));
 }
 
 static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
_

Patches currently in -mm which might be from vbabka@suse.cz are

mm-slub-fix-slub_debug-disablement-for-list-of-slabs.patch
mm-slub-dont-call-flush_all-from-slab_debug_trace_open.patch
mm-slub-allocate-private-object-map-for-debugfs-listings.patch
mm-slub-allocate-private-object-map-for-validate_slab_cache.patch
mm-slub-dont-disable-irq-for-debug_check_no_locks_freed.patch
mm-slub-remove-redundant-unfreeze_partials-from-put_cpu_partial.patch
mm-slub-unify-cmpxchg_double_slab-and-__cmpxchg_double_slab.patch
mm-slub-extract-get_partial-from-new_slab_objects.patch
mm-slub-dissolve-new_slab_objects-into-___slab_alloc.patch
mm-slub-return-slab-page-from-get_partial-and-set-c-page-afterwards.patch
mm-slub-restructure-new-page-checks-in-___slab_alloc.patch
mm-slub-simplify-kmem_cache_cpu-and-tid-setup.patch
mm-slub-move-disabling-enabling-irqs-to-___slab_alloc.patch
mm-slub-do-initial-checks-in-___slab_alloc-with-irqs-enabled.patch
mm-slub-move-disabling-irqs-closer-to-get_partial-in-___slab_alloc.patch
mm-slub-restore-irqs-around-calling-new_slab.patch
mm-slub-validate-slab-from-partial-list-or-page-allocator-before-making-it-cpu-slab.patch
mm-slub-check-new-pages-with-restored-irqs.patch
mm-slub-stop-disabling-irqs-around-get_partial.patch
mm-slub-move-reset-of-c-page-and-freelist-out-of-deactivate_slab.patch
mm-slub-make-locking-in-deactivate_slab-irq-safe.patch
mm-slub-call-deactivate_slab-without-disabling-irqs.patch
mm-slub-move-irq-control-into-unfreeze_partials.patch
mm-slub-discard-slabs-in-unfreeze_partials-without-irqs-disabled.patch
mm-slub-detach-whole-partial-list-at-once-in-unfreeze_partials.patch
mm-slub-separate-detaching-of-partial-list-in-unfreeze_partials-from-unfreezing.patch
mm-slub-only-disable-irq-with-spin_lock-in-__unfreeze_partials.patch
mm-slub-dont-disable-irqs-in-slub_cpu_dead.patch
mm-slab-make-flush_slab-possible-to-call-with-irqs-enabled.patch
mm-slub-optionally-save-restore-irqs-in-slab_lock.patch
mm-slub-make-slab_lock-disable-irqs-with-preempt_rt.patch
mm-slub-protect-put_cpu_partial-with-disabled-irqs-instead-of-cmpxchg.patch
mm-slub-use-migrate_disable-on-preempt_rt.patch
mm-slub-convert-kmem_cpu_slab-protection-to-local_lock.patch