pm24.git/kernel/rcu/tree.c, branch v5.6

Merge branches 'doc.2019.12.10a', 'exp.2019.12.09a', 'fixes.2020.01.24a', 'kfree_rcu.2020.01.24a', 'list.2020.01.10a', 'preempt.2020.01.24a' and 'torture.2019.12.09a' into HEAD

2020-01-24T18:37:27Z

doc.2019.12.10a: Documentations updates exp.2019.12.09a: Expedited grace-period updates fixes.2020.01.24a: Miscellaneous fixes kfree_rcu.2020.01.24a: Batch kfree_rcu() work list.2020.01.10a: RCU-protected-list updates preempt.2020.01.24a: Preemptible RCU updates torture.2019.12.09a: Torture-test updates

rcu: Remove unused stop-machine #include

2020-01-24T18:33:52Z

Long ago, RCU used the stop-machine mechanism to implement expedited grace periods, but no longer does so. This commit therefore removes the no-longer-needed #includes of linux/stop_machine.h. Link: https://lwn.net/Articles/805317/ Reported-by: Viresh Kumar Signed-off-by: Paul E. McKenney

rcu: Switch force_qs_rnp() to for_each_leaf_node_cpu_mask()

2020-01-24T18:33:51Z

Currently, force_qs_rnp() uses a for_each_leaf_node_possible_cpu() loop containing a check of the current CPU's bit in ->qsmask. This works, but this commit saves three lines by instead using for_each_leaf_node_cpu_mask(), which combines the functionality of for_each_leaf_node_possible_cpu() and leaf_node_cpu_bit(). This commit also replaces the use of the local variable "bit" with rdp->grpmask. Signed-off-by: Paul E. McKenney

rcu: Move gp_state_names[] and gp_state_getname() to tree_stall.h

2020-01-24T18:33:45Z

Only tree_stall.h needs to get name from GP state, so this commit moves the gp_state_names[] array and the gp_state_getname() from kernel/rcu/tree.h and kernel/rcu/tree.c, respectively, to kernel/rcu/tree_stall.h. While moving gp_state_names[], this commit uses the GCC syntax to ensure that the right string is associated with the right CPP macro. Signed-off-by: Lai Jiangshan Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

rcu: Fix tracepoint tracking RCU CPU kthread utilization

2020-01-24T18:33:31Z

In the call to trace_rcu_utilization() at the start of the loop in rcu_cpu_kthread(), "rcu_wait" is incorrect, plus this trace event needs to be hoisted above the loop to balance with either the "rcu_wait" or "rcu_yield", depending on how the loop exits. This commit therefore makes these changes. Signed-off-by: Lai Jiangshan Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

rcu: Avoid tick_dep_set_cpu() misordering

2020-01-24T18:27:33Z

In the current code, rcu_nmi_enter_common() might decide to turn on the tick using tick_dep_set_cpu(), but be delayed just before doing so. Then the grace-period kthread might notice that the CPU in question had in fact gone through a quiescent state, thus turning off the tick using tick_dep_clear_cpu(). The later invocation of tick_dep_set_cpu() would then incorrectly leave the tick on. This commit therefore enlists the aid of the leaf rcu_node structure's ->lock to ensure that decisions to enable or disable the tick are carried out before they can be reversed. Signed-off-by: Paul E. McKenney

rcu: Rename some instance of CONFIG_PREEMPTION to CONFIG_PREEMPT_RCU

2020-01-24T18:26:28Z

CONFIG_PREEMPTION and CONFIG_PREEMPT_RCU are always identical, but some code depends on CONFIG_PREEMPTION to access to rcu_preempt functionality. This patch changes CONFIG_PREEMPTION to CONFIG_PREEMPT_RCU in these cases. Signed-off-by: Lai Jiangshan Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

rcu: Remove kfree_call_rcu_nobatch()

2020-01-24T18:24:31Z

Now that the kfree_rcu() special-casing has been removed from tree RCU, this commit removes kfree_call_rcu_nobatch() since it is no longer needed. Signed-off-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney

rcu: Remove kfree_rcu() special casing and lazy-callback handling

2020-01-24T18:24:31Z

This commit removes kfree_rcu() special-casing and the lazy-callback handling from Tree RCU. It moves some of this special casing to Tiny RCU, the removal of which will be the subject of later commits. This results in a nice negative delta. Suggested-by: Paul E. McKenney Signed-off-by: Joel Fernandes (Google) [ paulmck: Add slab.h #include, thanks to kbuild test robot . ] Signed-off-by: Paul E. McKenney

rcu: Add support for debug_objects debugging for kfree_rcu()

2020-01-24T18:24:31Z

This commit applies RCU's debug_objects debugging to the new batched kfree_rcu() implementations. The object is queued at the kfree_rcu() call and dequeued during reclaim. Tested that enabling CONFIG_DEBUG_OBJECTS_RCU_HEAD successfully detects double kfree_rcu() calls. Signed-off-by: Joel Fernandes (Google) [ paulmck: Fix IRQ per kbuild test robot feedback. ] Signed-off-by: Paul E. McKenney