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[PATCH] Deprecate synchronize_kernel, GPL replacement

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The synchronize_kernel() primitive is used for quite a few different purposes:
waiting for RCU readers, waiting for NMIs, waiting for interrupts, and so on.
This makes RCU code harder to read, since synchronize_kernel() might or might
not have matching rcu_read_lock()s.  This patch creates a new
synchronize_rcu() that is to be used for RCU readers and a new
synchronize_sched() that is used for the rest.  These two new primitives
currently have the same implementation, but this is might well change with
additional real-time support.  Both new primitives are GPL-only, the old
primitive is deprecated.

Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Paul E. McKenney 2005-05-01 08:59:04 -07:00 • committed by Linus Torvalds
parent 512345be25
commit 9b06e81898
2 changed files with 34 additions and 5 deletions
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23
include/linux/rcupdate.h
View file

@ -157,9 +157,9 @@ static inline int rcu_pending(int cpu)
/**
* rcu_read_lock - mark the beginning of an RCU read-side critical section.
*
* When synchronize_kernel() is invoked on one CPU while other CPUs
* When synchronize_rcu() is invoked on one CPU while other CPUs
* are within RCU read-side critical sections, then the
* synchronize_kernel() is guaranteed to block until after all the other
* synchronize_rcu() is guaranteed to block until after all the other
* CPUs exit their critical sections. Similarly, if call_rcu() is invoked
* on one CPU while other CPUs are within RCU read-side critical
* sections, invocation of the corresponding RCU callback is deferred
@ -256,6 +256,21 @@ static inline int rcu_pending(int cpu)
(p) = (v); \
})
/**
* synchronize_sched - block until all CPUs have exited any non-preemptive
* kernel code sequences.
*
* This means that all preempt_disable code sequences, including NMI and
* hardware-interrupt handlers, in progress on entry will have completed
* before this primitive returns. However, this does not guarantee that
* softirq handlers will have completed, since in some kernels
*
* This primitive provides the guarantees made by the (deprecated)
* synchronize_kernel() API. In contrast, synchronize_rcu() only
* guarantees that rcu_read_lock() sections will have completed.
*/
#define synchronize_sched() synchronize_rcu()
extern void rcu_init(void);
extern void rcu_check_callbacks(int cpu, int user);
extern void rcu_restart_cpu(int cpu);
@ -265,7 +280,9 @@ extern void FASTCALL(call_rcu(struct rcu_head *head,
void (*func)(struct rcu_head *head)));
extern void FASTCALL(call_rcu_bh(struct rcu_head *head,
void (*func)(struct rcu_head *head)));
extern void synchronize_kernel(void);
extern __deprecated_for_modules void synchronize_kernel(void);
extern void synchronize_rcu(void);
void synchronize_idle(void);
#endif /* __KERNEL__ */
#endif /* __LINUX_RCUPDATE_H */