user/sven/linux.git/kernel/srcu.c, branch v3.10

srcu: use ACCESS_ONCE() to access sp->completed in srcu_read_lock()

2013-02-07T23:19:36Z

The old SRCU implementation loads sp->completed within an RCU-sched section, courtesy of preempt_disable(). This was required due to the use of synchronize_sched() in the old implemenation's synchronize_srcu(). However, the new implementation does not rely on synchronize_sched(), so it in turn does not require the load of sp->completed and the ->c[] counter to be in a single preempt-disabled region of code. This commit therefore moves the sp->completed access outside of the preempt-disabled region and applies ACCESS_ONCE(). The resulting code is almost as the same as before, but it removes the now-misleading rcu_dereference_index_check() call. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

srcu: Update synchronize_srcu_expedited()'s comments

2013-02-07T23:17:45Z

Because synchronize_srcu_expedited() no longer uses synchronize_rcu_sched_expedited(), synchronize_srcu_expedited() no longer indirectly acquires any CPU-hotplug-related locks. This commit therefore updates the comments accordingly. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

srcu: Update synchronize_srcu()'s comments

2013-02-07T23:17:01Z

The core of SRCU is changed, but synchronize_srcu()'s comments describe the old algorithm. This commit therefore updates them to match the new algorithm. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

srcu: Simple cleanup for cleanup_srcu_struct()

2013-02-07T23:10:10Z

Pack six lines of code into two lines. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

srcu: Add might_sleep() annotation to synchronize_srcu()

2013-02-07T23:08:19Z

Although synchronize_srcu() can sleep, it will not sleep if the fast path succeeds, which means that illegal use of synchronize_rcu() might go unnoticed. This commit therefore adds might_sleep(), which unconditionally catches illegal use of synchronize_rcu() from atomic context. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

srcu: Simplify __srcu_read_unlock() via this_cpu_dec()

2013-02-07T23:06:25Z

This commit replaces disabling of preemption and decrement of a per-CPU variable with this_cpu_dec(), which avoids preemption disabling on x86 and shortens the code on all platforms. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

Merge branches 'urgent.2012.10.27a', 'doc.2012.11.16a', 'fixes.2012.11.13a', 'srcu.2012.10.27a', 'stall.2012.11.13a', 'tracing.2012.11.08a' and 'idle.2012.10.24a' into HEAD

2012-11-16T17:59:58Z

urgent.2012.10.27a: Fix for RCU user-mode transition (already in -tip). doc.2012.11.08a: Documentation updates, most notably codifying the memory-barrier guarantees inherent to grace periods. fixes.2012.11.13a: Miscellaneous fixes. srcu.2012.10.27a: Allow statically allocated and initialized srcu_struct structures (courtesy of Lai Jiangshan). stall.2012.11.13a: Add more diagnostic information to RCU CPU stall warnings, also decrease from 60 seconds to 21 seconds. hotplug.2012.11.08a: Minor updates to CPU hotplug handling. tracing.2012.11.08a: Improved debugfs tracing, courtesy of Michael Wang. idle.2012.10.24a: Updates to RCU idle/adaptive-idle handling, including a boot parameter that maps normal grace periods to expedited. Resolved conflict in kernel/rcutree.c due to side-by-side change.

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

srcu: Credit Lai Jiangshan with SRCU rewrite

2012-10-23T21:54:41Z

Lai Jiangshan rewrote SRCU, so this commit ensures that he gets his proper share of blame^Wcredit. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

rcu: Add a module parameter to force use of expedited RCU primitives

2012-10-23T21:54:08Z

There have been some embedded applications that would benefit from use of expedited grace-period primitives. In some ways, this is similar to synchronize_net() doing either a normal or an expedited grace period depending on lock state, but with control outside of the kernel. This commit therefore adds rcu_expedited boot and sysfs parameters that cause the kernel to substitute expedited primitives for the normal grace-period primitives. [ paulmck: Add trace/event/rcu.h to kernel/srcu.c to avoid build error. Get rid of infinite loop through contention path.] Signed-off-by: Antti P Miettinen Signed-off-by: Paul E. McKenney