idr: make idr_find rcu-safe (f9c46d6e) · Commits · 戴 / test

include/linux/idr.h

+16 −0

Original line number	Diff line number	Diff line
		@@ -79,6 +79,22 @@ struct idr {

		#define _idr_rc_to_errno(rc) ((rc) == -1 ? -EAGAIN : -ENOSPC)

		/**
		* idr synchronization (stolen from radix-tree.h)
		*
		* idr_find() is able to be called locklessly, using RCU. The caller must
		* ensure calls to this function are made within rcu_read_lock() regions.
		* Other readers (lock-free or otherwise) and modifications may be running
		* concurrently.
		*
		* It is still required that the caller manage the synchronization and
		* lifetimes of the items. So if RCU lock-free lookups are used, typically
		* this would mean that the items have their own locks, or are amenable to
		* lock-free access; and that the items are freed by RCU (or only freed after
		* having been deleted from the idr tree and a synchronize_rcu() grace
		* period).
		*/

		/*
		* This is what we export.
		*/

+6 −5

Original line number	Diff line number	Diff line
		@@ -456,7 +456,8 @@ EXPORT_SYMBOL(idr_destroy);
		* return indicates that @id is not valid or you passed %NULL in
		* idr_get_new().
		*
		* The caller must serialize idr_find() vs idr_get_new() and idr_remove().
		* This function can be called under rcu_read_lock(), given that the leaf
		* pointers lifetimes are correctly managed.
		*/
		void idr_find(struct idr idp, int id)
		{
		@@ -464,7 +465,7 @@ void idr_find(struct idr idp, int id)
		struct idr_layer *p;

		n = idp->layers * IDR_BITS;
		p = idp->top;
		p = rcu_dereference(idp->top);

		/* Mask off upper bits we don't use for the search. */
		id &= MAX_ID_MASK;
		@@ -474,7 +475,7 @@ void idr_find(struct idr idp, int id)

		while (n > 0 && p) {
		n -= IDR_BITS;
		p = p->ary[(id >> n) & IDR_MASK];
		p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
		}
		return((void *)p);
		}
		@@ -507,7 +508,7 @@ int idr_for_each(struct idr *idp,
		struct idr_layer **paa = &pa[0];

		n = idp->layers * IDR_BITS;
		p = idp->top;
		p = rcu_dereference(idp->top);
		max = 1 << n;

		id = 0;
		@@ -515,7 +516,7 @@ int idr_for_each(struct idr *idp,
		while (n > 0 && p) {
		n -= IDR_BITS;
		*paa++ = p;
		p = p->ary[(id >> n) & IDR_MASK];
		p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
		}

		if (p) {