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radix-tree: use local locks 

The preload functionality uses per-CPU variables and preempt-disable to
ensure that it does not switch CPUs during its usage. This patch adds
local_locks() instead preempt_disable() for the same purpose and to
remain preemptible on -RT.

Cc: stable-rt@vger.kernel.org
Reported-and-debugged-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
This commit is contained in:
Sebastian Andrzej Siewior 2017-01-25 16:34:27 +01:00 committed by Alibek Omarov
parent f7d6ec8d74
commit 8d2a55bcd6
3 changed files with 23 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/idr.h
View File

@ -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.

6
include/linux/radix-tree.h
View File

@ -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);

28
lib/radix-tree.c
View File

@ -26,7 +26,7 @@
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/xarray.h>
#include <linux/locallock.h>
/*
* Radix tree node cache.
@ -72,6 +72,7 @@ struct radix_tree_preload {
struct radix_tree_node *nodes;
};
static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
static DEFINE_LOCAL_IRQ_LOCK(radix_tree_preloads_lock);
static inline struct radix_tree_node *entry_to_node(void *ptr)
{
@ -269,12 +270,13 @@ radix_tree_node_alloc(gfp_t gfp_mask, struct radix_tree_node *parent,
* succeed in getting a node here (and never reach
* kmem_cache_alloc)
*/
rtp = this_cpu_ptr(&radix_tree_preloads);
rtp = &get_locked_var(radix_tree_preloads_lock, radix_tree_preloads);
if (rtp->nr) {
ret = rtp->nodes;
rtp->nodes = ret->parent;
rtp->nr--;
}
put_locked_var(radix_tree_preloads_lock, radix_tree_preloads);
/*
* Update the allocation stack trace as this is more useful
* for debugging.
@ -340,14 +342,14 @@ 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;
@ -389,11 +391,17 @@ 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)
{
@ -1478,10 +1486,16 @@ 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)