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rcu: Don't redundantly disable irqs in rcu_irq_{enter,exit}()

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This commit replaces a local_irq_save()/local_irq_restore() pair with
a lockdep assertion that interrupts are already disabled.  This should
remove the corresponding overhead from the interrupt entry/exit fastpaths.

This change was inspired by the fact that Iftekhar Ahmed's mutation
testing showed that removing rcu_irq_enter()'s call to local_ird_restore()
had no effect, which might indicate that interrupts were always enabled
anyway.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2015-10-31 00:59:01 -07:00
parent d117c8aa1d
commit 7c9906ca5e
5 changed files with 40 additions and 10 deletions
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4
include/linux/tracepoint.h
View file

@ -171,8 +171,8 @@ extern void syscall_unregfunc(void);
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond), \
rcu_irq_enter(), \
rcu_irq_exit()); \
rcu_irq_enter_irqson(), \
rcu_irq_exit_irqson()); \
}
#else
#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)