user/sven/linux.git/include/linux/srcu.h, branch v3.4.40

rcu: Convert WARN_ON_ONCE() in rcu_lock_acquire() to lockdep

2012-02-21T17:06:09Z

The WARN_ON_ONCE() in rcu_lock_acquire() results in infinite recursion on S390, and also doesn't print very much information. Remove this. Updated patch to add lockdep-RCU assertions to RCU's read-side primitives. Signed-off-by: Heiko Carstens Signed-off-by: Paul E. McKenney

rcu: Check for illegal use of RCU from offlined CPUs

2012-02-21T17:06:03Z

Although it is legal to use RCU during early boot, it is anything but legal to use RCU at runtime from an offlined CPU. After all, RCU explicitly ignores offlined CPUs. This commit therefore adds checks for runtime use of RCU from offlined CPUs. These checks are not perfect, in particular, they can be subverted through use of things like rcu_dereference_raw(). Note that it is not possible to put checks in rcu_read_lock() and friends due to the fact that these primitives are used in code that might be used under either RCU or lock-based protection, which means that checking rcu_read_lock() gets you fat piles of false positives. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney

rcu: Document same-context read-side constraints

2011-12-11T18:32:06Z

The intent is that a given RCU read-side critical section be confined to a single context. For example, it is illegal to invoke rcu_read_lock() in an exception handler and then invoke rcu_read_unlock() from the context of the task that received the exception. Suggested-by: Peter Zijlstra Signed-off-by: Paul E. McKenney

rcu: Introduce raw SRCU read-side primitives

2011-12-11T18:31:40Z

The RCU implementations, including SRCU, are designed to be used in a lock-like fashion, so that the read-side lock and unlock primitives must execute in the same context for any given read-side critical section. This constraint is enforced by lockdep-RCU. However, there is a need to enter an SRCU read-side critical section within the context of an exception and then exit in the context of the task that encountered the exception. The cost of this capability is that the read-side operations incur the overhead of disabling interrupts. Note that although the current implementation allows a given read-side critical section to be entered by one task and then exited by another, all known possible implementations that allow this have scalability problems. Therefore, a given read-side critical section must be exited by the same task that entered it, though perhaps from an interrupt or exception handler running within that task's context. But if you are thinking in terms of interrupt handlers, make sure that you have considered the possibility of threaded interrupt handlers. Credit goes to Peter Zijlstra for suggesting use of the existing _raw suffix to indicate disabling lockdep over the earlier "bulkref" names. Requested-by: Srikar Dronamraju Signed-off-by: Paul E. McKenney Tested-by: Srikar Dronamraju

rcu: Make srcu_read_lock_held() call common lockdep-enabled function

2011-12-11T18:31:34Z

A common debug_lockdep_rcu_enabled() function is used to check whether RCU lockdep splats should be reported, but srcu_read_lock() does not use it. This commit therefore brings srcu_read_lock_held() up to date. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett

rcu: Warn when srcu_read_lock() is used in an extended quiescent state

2011-12-11T18:31:33Z

Catch SRCU up to the other variants of RCU by making PROVE_RCU complain if either srcu_read_lock() or srcu_read_lock_held() are used from within RCU-idle mode. Frederic reworked this to allow for the new versions of his patches that check for extended quiescent states. Signed-off-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett

rcu: Upgrade srcu_read_lock() docbook about SRCU grace periods

2010-08-20T16:00:15Z

It is illegal to wait for an SRCU grace period while within the corresponding flavor of SRCU read-side critical section. Therefore, this commit updates the srcu_read_lock() docbook accordingly. Signed-off-by: Paul E. McKenney

rcu: define __rcu address space modifier for sparse

2010-08-20T00:17:59Z

This commit provides definitions for the __rcu annotation defined earlier. This annotation permits sparse to check for correct use of RCU-protected pointers. If a pointer that is annotated with __rcu is accessed directly (as opposed to via rcu_dereference(), rcu_assign_pointer(), or one of their variants), sparse can be made to complain. To enable such complaints, use the new default-disabled CONFIG_SPARSE_RCU_POINTER kernel configuration option. Please note that these sparse complaints are intended to be a debugging aid, -not- a code-style-enforcement mechanism. There are special rcu_dereference_protected() and rcu_access_pointer() accessors for use when RCU read-side protection is not required, for example, when no other CPU has access to the data structure in question or while the current CPU hold the update-side lock. This patch also updates a number of docbook comments that were showing their age. Signed-off-by: Arnd Bergmann Signed-off-by: Paul E. McKenney Cc: Christopher Li Reviewed-by: Josh Triplett

rcu: make SRCU usable in modules

2010-05-10T18:08:35Z

Add a #include for mutex.h to allow SRCU to be more easily used in kernel modules. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

rcu: Fix bogus CONFIG_PROVE_LOCKING in comments to reflect reality.

2010-05-10T18:08:32Z

It is CONFIG_DEBUG_LOCK_ALLOC rather than CONFIG_PROVE_LOCKING, so fix it. Signed-off-by: Paul E. McKenney