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rcu: Rearrange locking in rcu_start_gp() 

If CPUs are to give prior notice of needed grace periods, it will be
necessary to invoke rcu_start_gp() without dropping the root rcu_node
structure's ->lock.  This commit takes a first step in this direction
by moving the release of this lock to the end of rcu_start_gp().

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2012-12-29 14:52:41 -08:00 committed by Paul E. McKenney
parent c0f4dfd4f9
commit b92db6cb7e
1 changed files with 2 additions and 4 deletions
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6
kernel/rcutree.c
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@ -1521,16 +1521,14 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
raw_spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
rsp->gp_flags = RCU_GP_FLAG_INIT;
raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */
/* Ensure that CPU is aware of completion of last grace period. */
rcu_process_gp_end(rsp, rdp);
local_irq_restore(flags);
__rcu_process_gp_end(rsp, rdp->mynode, rdp);
/* Wake up rcu_gp_kthread() to start the grace period. */
wake_up(&rsp->gp_wq);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
/*