pm24.git/kernel/rcu/tree_plugin.h, branch v4.3-rc6

Merge branches 'fixes.2015.07.22a' and 'initexp.2015.08.04a' into HEAD

2015-08-04T15:40:58Z

fixes.2015.07.22a: Miscellaneous fixes. initexp.2015.08.04a: Initialization and expedited updates. (Single branch due to conflicts.)

rcu: Don't disable CPU hotplug during OOM notifiers

2015-07-22T22:27:43Z

RCU's rcu_oom_notify() disables CPU hotplug in order to stabilize the list of online CPUs, which it traverses. However, this is completely pointless because smp_call_function_single() will quietly fail if invoked on an offline CPU. Because the count of requests is incremented in the rcu_oom_notify_cpu() function that is remotely invoked, everything works nicely even in the face of concurrent CPU-hotplug operations. Furthermore, in recent kernels, invoking get_online_cpus() from an OOM notifier can result in deadlock. This commit therefore removes the call to get_online_cpus() and put_online_cpus() from rcu_oom_notify(). Reported-by: Marcin Ślusarz Reported-by: David Rientjes Signed-off-by: Paul E. McKenney Acked-by: David Rientjes Tested-by: Marcin Ślusarz

rcu: Rename rcu_lockdep_assert() to RCU_LOCKDEP_WARN()

2015-07-22T22:27:32Z

This commit renames rcu_lockdep_assert() to RCU_LOCKDEP_WARN() for consistency with the WARN() series of macros. This also requires inverting the sense of the conditional, which this commit also does. Reported-by: Ingo Molnar Signed-off-by: Paul E. McKenney Reviewed-by: Ingo Molnar

rcu: Fix obsolete priority-boosting comment

2015-07-22T22:27:28Z

Tasks are no longer migrated to the root rcu_node, so there is no longer any need for a boost kthread for the root rcu_node, and there no longer is such a kthread. This commit therefore fixes the comment in rcu_boost_kthread()'s header to reflect this new reality. Signed-off-by: Paul E. McKenney

rcu: Consolidate last open-coded expedited memory barrier

2015-07-17T21:58:59Z

One of the requirements on RCU grace periods is that if there is a causal chain of operations that starts after one grace period and ends before another grace period, then the two grace periods must be serialized. There has been (and might still be) code that relies on this, for example, certain types of reference-counting code that does a call_rcu() within an RCU callback function. This requirement is why there is an smp_mb() at the end of both synchronize_sched_expedited() and synchronize_rcu_expedited(). However, this is the only smp_mb() in these functions, so it would be nicer to consolidate it into rcu_exp_gp_seq_end(). This commit does just that. Signed-off-by: Paul E. McKenney

rcu: Use funnel locking for synchronize_rcu_expedited()'s polling loop

2015-07-17T21:58:56Z

This commit gets rid of synchronize_rcu_expedited()'s mutex_trylock() polling loop in favor of the funnel-locking scheme that was abstracted from synchronize_sched_expedited(). Signed-off-by: Paul E. McKenney

rcu: Make synchronize_rcu_expedited() use sequence-counter scheme

2015-07-17T21:58:52Z

Although synchronize_rcu_expedited() uses a sequence-counter scheme, it is based on a single increment per grace period, which means that tasks piggybacking off of concurrent grace periods may be forced to wait longer than necessary. This commit therefore applies the new sequence-count functions developed for synchronize_sched_expedited() to speed things up a bit and to consolidate the sequence-counter implementation. Signed-off-by: Paul E. McKenney

rcu: Remove CONFIG_RCU_CPU_STALL_INFO

2015-07-17T21:58:44Z

The CONFIG_RCU_CPU_STALL_INFO has been default-y for a couple of releases with no complaints, so it is time to eliminate this Kconfig option entirely, so that the long-form RCU CPU stall warnings cannot be disabled. This commit does just that. Signed-off-by: Paul E. McKenney

rcu: Stop disabling CPU hotplug in synchronize_rcu_expedited()

2015-07-17T21:58:42Z

The fact that tasks could be migrated from leaf to root rcu_node structures meant that synchronize_rcu_expedited() had to disable CPU hotplug. However, tasks now stay put, so this commit removes the CPU-hotplug disabling from synchronize_rcu_expedited(). Signed-off-by: Paul E. McKenney

rcu: Simplify arithmetic to calculate number of RCU nodes

2015-07-15T21:45:21Z

This update makes arithmetic to calculate number of RCU nodes more straight and easy to read. Cc: "Paul E. McKenney" Cc: Steven Rostedt Signed-off-by: Alexander Gordeev Signed-off-by: Paul E. McKenney