rcu: Provide API to suppress stall warnings while sysrc runs (61f38db3) · Commits · 戴 / test

Some sysrq handlers can run for a long time, because they dump a lot of data onto a serial console. Having RCU stall warnings pop up in the middle of them only makes the problem worse. This commit provides rcu_sysrq_start() and rcu_sysrq_end() APIs to temporarily suppress RCU CPU stall warnings while a sysrq request is handled. Signed-off-by:

Rik van Riel <riel@redhat.com> [ paulmck: Fix TINY_RCU build error. ] Signed-off-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com>

include/linux/rcupdate.h

+12 −0

Original line number	Diff line number	Diff line
		@@ -248,6 +248,18 @@ void rcu_idle_exit(void);
		void rcu_irq_enter(void);
		void rcu_irq_exit(void);

		#ifdef CONFIG_RCU_STALL_COMMON
		void rcu_sysrq_start(void);
		void rcu_sysrq_end(void);
		#else /* #ifdef CONFIG_RCU_STALL_COMMON */
		static inline void rcu_sysrq_start(void)
		{
		}
		static inline void rcu_sysrq_end(void)
		{
		}
		#endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */

		#ifdef CONFIG_RCU_USER_QS
		void rcu_user_enter(void);
		void rcu_user_exit(void);

kernel/rcu/update.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -320,6 +320,18 @@ int rcu_jiffies_till_stall_check(void)
		return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
		}

		void rcu_sysrq_start(void)
		{
		if (!rcu_cpu_stall_suppress)
		rcu_cpu_stall_suppress = 2;
		}

		void rcu_sysrq_end(void)
		{
		if (rcu_cpu_stall_suppress == 2)
		rcu_cpu_stall_suppress = 0;
		}

		static int rcu_panic(struct notifier_block this, unsigned long ev, void ptr)
		{
		rcu_cpu_stall_suppress = 1;

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