user/sven/linux.git/kernel/rcu/tree_trace.c, branch v4.9.99

rcu: Drive expedited grace periods from workqueue

2016-08-22T16:30:25Z

The current implementation of expedited grace periods has the user task drive the grace period. This works, but has downsides: (1) The user task must awaken tasks piggybacking on this grace period, which can result in latencies rivaling that of the grace period itself, and (2) User tasks can receive signals, which interfere with RCU CPU stall warnings. This commit therefore uses workqueues to drive the grace periods, so that the user task need not do the awakening. A subsequent commit will remove the now-unnecessary code allowing for signals. Signed-off-by: Paul E. McKenney

rcu: Shorten expedited_workdone* to exp_workdone*

2016-03-31T20:34:08Z

Just a name change to save a few lines and a bit of typing. Signed-off-by: Paul E. McKenney

rcu: Remove expedited GP funnel-lock bypass

2016-03-31T20:34:07Z

Commit #cdacbe1f91264 ("rcu: Add fastpath bypassing funnel locking") turns out to be a pessimization at high load because it forces a tree full of tasks to wait for an expedited grace period that they probably do not need. This commit therefore removes this optimization. Signed-off-by: Paul E. McKenney

Merge branches 'doc.2015.12.05a', 'exp.2015.12.07a', 'fixes.2015.12.07a', 'list.2015.12.04b' and 'torture.2015.12.05a' into HEAD

2015-12-08T01:02:54Z

doc.2015.12.05a: Documentation updates exp.2015.12.07a: Expedited grace-period updates fixes.2015.12.07a: Miscellaneous fixes list.2015.12.04b: Linked-list updates torture.2015.12.05a: Torture-test updates

kernel: Make rcu/tree_trace.c explicitly non-modular

2015-12-04T20:27:29Z

The Kconfig currently controlling compilation of this code is: init/Kconfig:config TREE_RCU_TRACE init/Kconfig: def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU ) ...meaning that it currently is not being built as a module by anyone. Lets remove the modular code that is essentially orphaned, so that when reading the file there is no doubt it is builtin-only. Since module_init translates to device_initcall in the non-modular case, the init ordering remains unchanged with this commit. We could consider moving this to an earlier initcall if desired. We don't replace module.h with init.h since the file already has that. We also delete the moduleparam.h include that is left over from commit 64db4cfff99c04cd5f550357edcc8780f96b54a2 (""Tree RCU": scalable classic RCU implementation") since it is not needed here either. We morph some tags like MODULE_AUTHOR into the comments at the top of the file for documentation purposes. Cc: "Paul E. McKenney" Cc: Josh Triplett Reviewed-by: Josh Triplett Cc: Steven Rostedt Cc: Mathieu Desnoyers Cc: Lai Jiangshan Signed-off-by: Paul Gortmaker Signed-off-by: Paul E. McKenney

rcu: Reduce expedited GP memory contention via per-CPU variables

2015-12-04T20:26:52Z

Currently, the piggybacked-work checks carried out by sync_exp_work_done() atomically increment a small set of variables (the ->expedited_workdone0, ->expedited_workdone1, ->expedited_workdone2, ->expedited_workdone3 fields in the rcu_state structure), which will form a memory-contention bottleneck given a sufficiently large number of CPUs concurrently invoking either synchronize_rcu_expedited() or synchronize_sched_expedited(). This commit therefore moves these for fields to the per-CPU rcu_data structure, eliminating the memory contention. The show_rcuexp() function also changes to sum up each field in the rcu_data structures. Signed-off-by: Paul E. McKenney

rcu: Add transitivity to remaining rcu_node ->lock acquisitions

2015-11-23T18:37:35Z

The rule is that all acquisitions of the rcu_node structure's ->lock must provide transitivity: The lock is not acquired that frequently, and sorting out exactly which required it and which did not would be a maintenance nightmare. This commit therefore supplies the needed transitivity to the remaining ->lock acquisitions. Reported-by: Peter Zijlstra Signed-off-by: Paul E. McKenney

Merge branches 'fixes.2015.10.06a' and 'exp.2015.10.07a' into HEAD

2015-10-07T23:05:21Z

exp.2015.10.07a: Reduce OS jitter of RCU-sched expedited grace periods. fixes.2015.10.06a: Miscellaneous fixes.

rcu: Finish folding ->fqs_state into ->gp_state

2015-10-06T18:15:59Z

Commit commit 4cdfc175c25c89ee ("rcu: Move quiescent-state forcing into kthread") started the process of folding the old ->fqs_state into ->gp_state, but did not complete it. This situation does not cause any malfunction, but can result in extremely confusing trace output. This commit completes this task of eliminating ->fqs_state in favor of ->gp_state. The old ->fqs_state was also used to decide when to collect dyntick-idle snapshots. For this purpose, we add a boolean variable into the kthread, which is set on the first call to rcu_gp_fqs() for a given grace period and clear otherwise. Signed-off-by: Petr Mladek Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett

rcu: Make ->cpu_no_qs be a union for aggregate OR

2015-09-21T04:16:21Z

This commit converts the rcu_data structure's ->cpu_no_qs field to a union. The bytewise side of this union allows individual access to indications as to whether this CPU needs to find a quiescent state for a normal (.norm) and/or expedited (.exp) grace period. The setwise side of the union allows testing whether or not a quiescent state is needed at all, for either type of grace period. For now, only .norm is used. A later commit will introduce the expedited usage. Signed-off-by: Paul E. McKenney