The radix-tree and idr preload mechanisms use preempt_disable() to protect the complete operation between xxx_preload() and xxx_preload_end().
As the code inside the preempt disabled section acquires regular spinlocks, which are converted to 'sleeping' spinlocks on a PREEMPT_RT kernel and eventually calls into a memory allocator, this conflicts with the RT semantics. Convert it to a local_lock which allows RT kernels to substitute them with a real per CPU lock. On non RT kernels this maps to preempt_disable() as before, but provides also lockdep coverage of the critical region. No functional change. Cc: Matthew Wilcox <[email protected]> Cc: [email protected] Signed-off-by: Sebastian Andrzej Siewior <[email protected]> --- include/linux/idr.h | 5 +---- include/linux/radix-tree.h | 6 +----- lib/radix-tree.c | 25 +++++++++++++++++++------ 3 files changed, 21 insertions(+), 15 deletions(-) diff --git a/include/linux/idr.h b/include/linux/idr.h index ac6e946b6767b..839da8f2f6f13 100644 --- a/include/linux/idr.h +++ b/include/linux/idr.h @@ -169,10 +169,7 @@ static inline bool idr_is_empty(const struct idr *idr) * Each idr_preload() should be matched with an invocation of this * function. See idr_preload() for details. */ -static inline void idr_preload_end(void) -{ - preempt_enable(); -} +void idr_preload_end(void); /** * idr_for_each_entry() - Iterate over an IDR's elements of a given type. diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index 63e62372443a5..040b1fd0ab940 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -226,6 +226,7 @@ unsigned int radix_tree_gang_lookup(const struct radix_tree_root *, unsigned int max_items); int radix_tree_preload(gfp_t gfp_mask); int radix_tree_maybe_preload(gfp_t gfp_mask); +void radix_tree_preload_end(void); void radix_tree_init(void); void *radix_tree_tag_set(struct radix_tree_root *, unsigned long index, unsigned int tag); @@ -243,11 +244,6 @@ unsigned int radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *, unsigned int max_items, unsigned int tag); int radix_tree_tagged(const struct radix_tree_root *, unsigned int tag); -static inline void radix_tree_preload_end(void) -{ - preempt_enable(); -} - void __rcu **idr_get_free(struct radix_tree_root *root, struct radix_tree_iter *iter, gfp_t gfp, unsigned long max); diff --git a/lib/radix-tree.c b/lib/radix-tree.c index 2ee6ae3b0ade0..8a44f7b85dfdc 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -20,6 +20,7 @@ #include <linux/kernel.h> #include <linux/kmemleak.h> #include <linux/percpu.h> +#include <linux/locallock.h> #include <linux/preempt.h> /* in_interrupt() */ #include <linux/radix-tree.h> #include <linux/rcupdate.h> @@ -27,7 +28,6 @@ #include <linux/string.h> #include <linux/xarray.h> - /* * Radix tree node cache. */ @@ -64,6 +64,7 @@ struct radix_tree_preload { struct radix_tree_node *nodes; }; static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, }; +static DEFINE_LOCAL_LOCK(radix_tree_preloads_lock); static inline struct radix_tree_node *entry_to_node(void *ptr) { @@ -332,14 +333,14 @@ static __must_check int __radix_tree_preload(gfp_t gfp_mask, unsigned nr) */ gfp_mask &= ~__GFP_ACCOUNT; - preempt_disable(); + local_lock(radix_tree_preloads_lock); rtp = this_cpu_ptr(&radix_tree_preloads); while (rtp->nr < nr) { - preempt_enable(); + local_unlock(radix_tree_preloads_lock); node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask); if (node == NULL) goto out; - preempt_disable(); + local_lock(radix_tree_preloads_lock); rtp = this_cpu_ptr(&radix_tree_preloads); if (rtp->nr < nr) { node->parent = rtp->nodes; @@ -381,11 +382,17 @@ int radix_tree_maybe_preload(gfp_t gfp_mask) if (gfpflags_allow_blocking(gfp_mask)) return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE); /* Preloading doesn't help anything with this gfp mask, skip it */ - preempt_disable(); + local_lock(radix_tree_preloads_lock); return 0; } EXPORT_SYMBOL(radix_tree_maybe_preload); +void radix_tree_preload_end(void) +{ + local_unlock(radix_tree_preloads_lock); +} +EXPORT_SYMBOL(radix_tree_preload_end); + static unsigned radix_tree_load_root(const struct radix_tree_root *root, struct radix_tree_node **nodep, unsigned long *maxindex) { @@ -1470,10 +1477,16 @@ EXPORT_SYMBOL(radix_tree_tagged); void idr_preload(gfp_t gfp_mask) { if (__radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE)) - preempt_disable(); + local_lock(radix_tree_preloads_lock); } EXPORT_SYMBOL(idr_preload); +void idr_preload_end(void) +{ + local_unlock(radix_tree_preloads_lock); +} +EXPORT_SYMBOL(idr_preload_end); + void __rcu **idr_get_free(struct radix_tree_root *root, struct radix_tree_iter *iter, gfp_t gfp, unsigned long max) -- 2.26.2
