user/sven/linux.git/include/linux/srcu.h, branch v4.2.4

rcu: Reverse rcu_dereference_check() conditions

2015-03-03T19:16:47Z

The rcu_dereference_check() family of primitives evaluates the RCU lockdep expression first, and only then evaluates the expression passed in. This works fine normally, but can potentially fail in environments (such as NMI handlers) where lockdep cannot be invoked. The problem is that even if the expression passed in is "1", the compiler would need to prove that the RCU lockdep expression (rcu_read_lock_held(), for example) is free of side effects in order to be able to elide it. Given that rcu_read_lock_held() is sometimes separately compiled, the compiler cannot always use this optimization. This commit therefore reverse the order of evaluation, so that the expression passed in is evaluated first, and the RCU lockdep expression is evaluated only if the passed-in expression evaluated to false, courtesy of the C-language short-circuit boolean evaluation rules. This compells the compiler to forego executing the RCU lockdep expression in cases where the passed-in expression evaluates to "1" at compile time, so that (for example) rcu_dereference_raw() can be guaranteed to execute safely within an NMI handler. Signed-off-by: Paul E. McKenney Acked-by: Peter Zijlstra (Intel)

rcu: Combine DEFINE_SRCU() and DEFINE_STATIC_SRCU()

2015-01-06T19:04:27Z

The DEFINE_SRCU() and DEFINE_STATIC_SRCU() definitions are quite similar, so this commit combines them, saving a bit of code and removing redundancy. Signed-off-by: Paul E. McKenney

rcu: Expand SRCU ->completed to 64 bits

2015-01-06T19:04:26Z

When rcutorture used only the low-order 32 bits of the grace-period number, it was not a problem for SRCU to use a 32-bit completed field. However, rcutorture now uses the full 64 bits on 64-bit systems, so this commit converts SRCU's ->completed field to unsigned long so as to provide 64 bits on 64-bit systems. Signed-off-by: Paul E. McKenney

rcu: Stop tracking FSF's postal address

2014-02-17T23:01:37Z

All of the RCU source files have the usual GPL header, which contains a long-obsolete postal address for FSF. To avoid the need to track the FSF office's movements, this commit substitutes the URL where GPL may be found. Reported-by: Greg KH Reported-by: Steven Rostedt Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett

srcu: API for barrier after srcu read unlock

2013-11-06T07:32:09Z

srcu read lock/unlock include a full memory barrier but that's an implementation detail. Add an API for make memory fencing explicit for users that need this barrier, to make sure we can change it as needed without breaking all users. Acked-by: "Paul E. McKenney" Reviewed-by: Paul E. McKenney Signed-off-by: Michael S. Tsirkin Signed-off-by: Gleb Natapov

rcu: Remove srcu_read_lock_raw() and srcu_read_unlock_raw().

2013-06-10T20:45:25Z

These interfaces never did get used, so this commit removes them, their rcutorture tests, and documentation referencing them. Signed-off-by: Paul E. McKenney Reviewed-by: Lai Jiangshan Reviewed-by: Josh Triplett

srcu: Remove checks preventing idle CPUs from calling srcu_read_lock()

2013-02-07T23:15:00Z

SRCU has its own statemachine and no longer relies on normal RCU. Its read-side critical section can now be used by an offline CPU, so this commit removes the check and the comments, reverting the SRCU portion of ff195cb6 (rcu: Warn when srcu_read_lock() is used in an extended quiescent state). It also makes the codes match the comments in whatisRCU.txt: g. Do you need read-side critical sections that are respected even though they are in the middle of the idle loop, during user-mode execution, or on an offlined CPU? If so, SRCU is the only choice that will work for you. [ paulmck: There is at least one remaining issue, namely use of lockdep with tracing enabled. ] Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

srcu: Remove checks preventing offline CPUs from calling srcu_read_lock()

2013-02-07T23:10:39Z

SRCU has its own statemachine and no longer relies on normal RCU. Its read-side critical section can now be used by an offline CPU, so this commit removes the check and the comments, reverting the SRCU portion of c0d6d01b (rcu: Check for illegal use of RCU from offlined CPUs). It also makes the code match the comments in whatisRCU.txt: g. Do you need read-side critical sections that are respected even though they are in the middle of the idle loop, during user-mode execution, or on an offlined CPU? If so, SRCU is the only choice that will work for you. [ paulmck: There is at least one remaining issue, namely use of lockdep with tracing enabled. ] Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

srcu: Add DEFINE_SRCU()

2012-10-27T22:38:29Z

In old days, we had two different API sets for dynamic-allocated per-CPU data and DEFINE_PER_CPU()-defined per_cpu data, and because SRCU used dynamic-allocated per-CPU data, its srcu_struct structures cannot be declared statically. This commit therefore introduces DEFINE_SRCU() and DEFINE_STATIC_SRCU() to allow statically declared SRCU structures, using the new static per-CPU interfaces. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney [ paulmck: Updated for __DELAYED_WORK_INITIALIZER() added argument, fixed whitespace issue. ]

srcu: Export process_srcu()

2012-10-23T21:54:42Z

Because process_srcu() will be used in DEFINE_SRCU(), which is a macro that could be expanded pretty much anywhere, it can no longer be static. Note that process_srcu() is still internal to srcu.h. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney