rcu: Export debug_init_rcu_head() and and debug_init_rcu_head() (546a9d85) · Commits · 戴 / test

Currently, call_rcu() relies on implicit allocation and initialization for the debug-objects handling of RCU callbacks. If you hammer the kernel hard enough with Sasha's modified version of trinity, you can end up with the sl*b allocators recursing into themselves via this implicit call_rcu() allocation. This commit therefore exports the debug_init_rcu_head() and debug_rcu_head_free() functions, which permits the allocators to allocated and pre-initialize the debug-objects information, so that there no longer any need for call_rcu() to do that initialization, which in turn prevents the recursion into the memory allocators. Reported-by:

Sasha Levin <sasha.levin@oracle.com> Suggested-by:

Thomas Gleixner <tglx@linutronix.de> Signed-off-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by:

Thomas Gleixner <tglx@linutronix.de> Looks-good-to: Christoph Lameter <cl@linux.com>

include/linux/rcupdate.h

+10 −0

Original line number	Diff line number	Diff line
		@@ -358,9 +358,19 @@ void wait_rcu_gp(call_rcu_func_t crf);
		* initialization.
		*/
		#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
		void init_rcu_head(struct rcu_head *head);
		void destroy_rcu_head(struct rcu_head *head);
		void init_rcu_head_on_stack(struct rcu_head *head);
		void destroy_rcu_head_on_stack(struct rcu_head *head);
		#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
		static inline void init_rcu_head(struct rcu_head *head)
		{
		}

		static inline void destroy_rcu_head(struct rcu_head *head)
		{
		}

		static inline void init_rcu_head_on_stack(struct rcu_head *head)
		{
		}

kernel/rcu/update.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -200,12 +200,12 @@ void wait_rcu_gp(call_rcu_func_t crf)
		EXPORT_SYMBOL_GPL(wait_rcu_gp);

		#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
		static inline void debug_init_rcu_head(struct rcu_head *head)
		void init_rcu_head(struct rcu_head *head)
		{
		debug_object_init(head, &rcuhead_debug_descr);
		}

		static inline void debug_rcu_head_free(struct rcu_head *head)
		void destroy_rcu_head(struct rcu_head *head)
		{
		debug_object_free(head, &rcuhead_debug_descr);
		}

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