Re: [RFC PATCH 4/5] RCU: Add TASK_RCU_OFFSET

[Peter Zijlstra]

On Fri, 2011-04-01 at 09:57 +0800, Lai Jiangshan wrote:
> 
> We are trying to use inlined read_read_[un]lock(), it is required that sched.h
> needs include rcupdate.h which causes many recursive including. Splitting rcupdate.h
> only does not help. 

You're not making any kind of sense there.

linux-2.6# cat kernel/sched_tmp.c 

#include <linux/sched.h>

linux-2.6# make kernel/sched_tmp.i
linux-2.6# awk '/^#/ { t=$0 } /rcu_read_lock/ { print t " " $0 }' kernel/sched_tmp.i
# 60 "/usr/src/linux-2.6/include/linux/rcupdate.h" static inline void __rcu_read_lock_bh(void)
# 60 "/usr/src/linux-2.6/include/linux/rcupdate.h" extern void __rcu_read_lock(void);
# 258 "/usr/src/linux-2.6/include/linux/rcupdate.h" static inline int rcu_read_lock_held(void)
# 258 "/usr/src/linux-2.6/include/linux/rcupdate.h" static inline int rcu_read_lock_bh_held(void)
# 258 "/usr/src/linux-2.6/include/linux/rcupdate.h" static inline int rcu_read_lock_sched_held(void)
# 559 "/usr/src/linux-2.6/include/linux/rcupdate.h" static inline void rcu_read_lock(void)
# 559 "/usr/src/linux-2.6/include/linux/rcupdate.h"  __rcu_read_lock();
# 600 "/usr/src/linux-2.6/include/linux/rcupdate.h" static inline void rcu_read_lock_bh(void)
# 600 "/usr/src/linux-2.6/include/linux/rcupdate.h"  __rcu_read_lock_bh();
# 627 "/usr/src/linux-2.6/include/linux/rcupdate.h" static inline void rcu_read_lock_sched(void)
# 627 "/usr/src/linux-2.6/include/linux/rcupdate.h" static inline __attribute__((no_instrument_function)) void rcu_read_lock_sched_notrace(void)
# 70 "/usr/src/linux-2.6/include/linux/srcu.h" int __srcu_read_lock(struct srcu_struct *sp) ;
# 103 "/usr/src/linux-2.6/include/linux/srcu.h" static inline int srcu_read_lock_held(struct srcu_struct *sp)
# 149 "/usr/src/linux-2.6/include/linux/srcu.h" static inline int srcu_read_lock(struct srcu_struct *sp)
# 149 "/usr/src/linux-2.6/include/linux/srcu.h"  int retval = __srcu_read_lock(sp);
# 1227 "/usr/src/linux-2.6/include/linux/sched.h"  int rcu_read_lock_nesting;
# 1786 "/usr/src/linux-2.6/include/linux/sched.h"  p->rcu_read_lock_nesting = 0;

There isn't a single rcu_read_lock() user in the include chain of
sched.h, therefore its possible to split rcupdate.h such that one part
includes the bits needed for sched.h and another part that includes
sched.h and provides rcu_read_lock().


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