Commit 1bb5f9b9 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu/nocb: Use separate flag to indicate disabled ->cblist 



NULLing the RCU_NEXT_TAIL pointer was a clever way to save a byte, but
forward-progress considerations would require that this pointer be both
NULL and non-NULL, which, absent a quantum-computer port of the Linux
kernel, simply won't happen.  This commit therefore creates as separate
->enabled flag to replace the current NULL checks.

[ paulmck: Add include files per 0day test robot and -next. ]
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.ibm.com>
parent 18cd8c93

include/linux/rcu_segcblist.h

+4 −0
Original line number Diff line number Diff line
@@ -14,6 +14,9 @@ 
#ifndef __INCLUDE_LINUX_RCU_SEGCBLIST_H

#define __INCLUDE_LINUX_RCU_SEGCBLIST_H



#include <linux/types.h>

#include <linux/atomic.h>



/* Simple unsegmented callback lists. */

struct rcu_cblist {

	struct rcu_head *head;
@@ -67,6 +70,7 @@ struct rcu_segcblist { 
	unsigned long gp_seq[RCU_CBLIST_NSEGS];

	long len;

	long len_lazy;

	u8 enabled;

};



#define RCU_SEGCBLIST_INITIALIZER(n) \

kernel/rcu/rcu_segcblist.c

+2 −1
Original line number Diff line number Diff line
@@ -58,6 +58,7 @@ void rcu_segcblist_init(struct rcu_segcblist *rsclp) 
		rsclp->tails[i] = &rsclp->head;

	rsclp->len = 0;

	rsclp->len_lazy = 0;

	rsclp->enabled = 1;

}



/*
@@ -69,7 +70,7 @@ void rcu_segcblist_disable(struct rcu_segcblist *rsclp) 
	WARN_ON_ONCE(!rcu_segcblist_empty(rsclp));

	WARN_ON_ONCE(rcu_segcblist_n_cbs(rsclp));

	WARN_ON_ONCE(rcu_segcblist_n_lazy_cbs(rsclp));

	rsclp->tails[RCU_NEXT_TAIL] = NULL;

	rsclp->enabled = 0;

}



/*

kernel/rcu/rcu_segcblist.h

+1 −1
Original line number Diff line number Diff line
@@ -63,7 +63,7 @@ static inline long rcu_segcblist_n_nonlazy_cbs(struct rcu_segcblist *rsclp) 
 */

static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)

{

	return !!rsclp->tails[RCU_NEXT_TAIL];

	return rsclp->enabled;

}



/*

kernel/rcu/tree_plugin.h

+1 −1
Original line number Diff line number Diff line
@@ -2189,8 +2189,8 @@ static bool init_nocb_callback_list(struct rcu_data *rdp) 
				rcu_segcblist_n_cbs(&rdp->cblist));

		atomic_long_set(&rdp->nocb_q_count_lazy,

				rcu_segcblist_n_lazy_cbs(&rdp->cblist));

		rcu_segcblist_init(&rdp->cblist);

	}

	rcu_segcblist_init(&rdp->cblist);

	rcu_segcblist_disable(&rdp->cblist);

	return true;

}

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