The following commit has been merged into the locking/core branch of tip: Commit-ID: cfa6705d89b6562f79c40c249f8d94073c4276e4 Gitweb: https://git.kernel.org/tip/cfa6705d89b6562f79c40c249f8d94073c4276e4 Author: Sebastian Andrzej Siewior <bige...@linutronix.de> AuthorDate: Wed, 27 May 2020 22:11:14 +02:00 Committer: Ingo Molnar <mi...@kernel.org> CommitterDate: Thu, 28 May 2020 10:31:09 +02:00
radix-tree: Use local_lock for protection 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. Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de> Signed-off-by: Ingo Molnar <mi...@kernel.org> Acked-by: Peter Zijlstra <pet...@infradead.org> Link: https://lore.kernel.org/r/20200527201119.1692513-3-bige...@linutronix.de --- include/linux/idr.h | 2 +- include/linux/radix-tree.h | 11 ++++++++++- lib/radix-tree.c | 20 +++++++++----------- 3 files changed, 20 insertions(+), 13 deletions(-) diff --git a/include/linux/idr.h b/include/linux/idr.h index ac6e946..3ade03e 100644 --- a/include/linux/idr.h +++ b/include/linux/idr.h @@ -171,7 +171,7 @@ static inline bool idr_is_empty(const struct idr *idr) */ static inline void idr_preload_end(void) { - preempt_enable(); + local_unlock(&radix_tree_preloads.lock); } /** diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index 63e6237..c2a9f7c 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -16,11 +16,20 @@ #include <linux/spinlock.h> #include <linux/types.h> #include <linux/xarray.h> +#include <linux/local_lock.h> /* Keep unconverted code working */ #define radix_tree_root xarray #define radix_tree_node xa_node +struct radix_tree_preload { + local_lock_t lock; + unsigned nr; + /* nodes->parent points to next preallocated node */ + struct radix_tree_node *nodes; +}; +DECLARE_PER_CPU(struct radix_tree_preload, radix_tree_preloads); + /* * The bottom two bits of the slot determine how the remaining bits in the * slot are interpreted: @@ -245,7 +254,7 @@ int radix_tree_tagged(const struct radix_tree_root *, unsigned int tag); static inline void radix_tree_preload_end(void) { - preempt_enable(); + local_unlock(&radix_tree_preloads.lock); } void __rcu **idr_get_free(struct radix_tree_root *root, diff --git a/lib/radix-tree.c b/lib/radix-tree.c index 2ee6ae3..34e406f 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/local_lock.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. */ @@ -58,12 +58,10 @@ struct kmem_cache *radix_tree_node_cachep; /* * Per-cpu pool of preloaded nodes */ -struct radix_tree_preload { - unsigned nr; - /* nodes->parent points to next preallocated node */ - struct radix_tree_node *nodes; +DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { + .lock = INIT_LOCAL_LOCK(lock), }; -static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, }; +EXPORT_PER_CPU_SYMBOL_GPL(radix_tree_preloads); static inline struct radix_tree_node *entry_to_node(void *ptr) { @@ -332,14 +330,14 @@ 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; @@ -381,7 +379,7 @@ 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); @@ -1470,7 +1468,7 @@ 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);
