user/sven/linux.git/kernel/rcu/tree_exp.h, branch v5.3.14

rcu: Add destroy_work_on_stack() to match INIT_WORK_ONSTACK()

2019-10-05T13:11:32Z

[ Upstream commit fbad01af8c3bb9618848abde8054ab7e0c2330fe ] The synchronize_rcu_expedited() function has an INIT_WORK_ONSTACK(), but lacks the corresponding destroy_work_on_stack(). This commit therefore adds destroy_work_on_stack(). Reported-by: Andrea Arcangeli Signed-off-by: Paul E. McKenney Acked-by: Andrea Arcangeli Signed-off-by: Sasha Levin

Merge branches 'consolidate.2019.05.28a', 'doc.2019.05.28a', 'fixes.2019.06.13a', 'srcu.2019.05.28a', 'sync.2019.05.28a' and 'torture.2019.05.28a' into HEAD

2019-06-19T16:21:46Z

consolidate.2019.05.28a: RCU flavor consolidation cleanups and optmizations. doc.2019.05.28a: Documentation updates. fixes.2019.06.13a: Miscellaneous fixes. srcu.2019.05.28a: SRCU updates. sync.2019.05.28a: RCU-sync flavor consolidation. torture.2019.05.28a: Torture-test updates.

rcu: Upgrade sync_exp_work_done() to smp_mb()

2019-06-13T22:33:19Z

The sync_exp_work_done() function uses smp_mb__before_atomic(), but there is no obvious atomic in the ensuing code. The ordering is absolutely required for grace periods to work correctly, so this commit upgrades the smp_mb__before_atomic() to smp_mb(). Fixes: 6fba2b3767ea ("rcu: Remove deprecated RCU debugfs tracing code") Reported-by: Andrea Parri Signed-off-by: Paul E. McKenney

rcu: Remove unused rdp local from synchronize_rcu_expedited()

2019-05-28T15:48:19Z

Because rdp is initialized but never used in synchronize_rcu_expedited(), this commit removes it. Signed-off-by: Jiang Biao Signed-off-by: Paul E. McKenney

rcu: Rename rcu_data's ->deferred_qs to ->exp_deferred_qs

2019-05-28T15:48:19Z

The rcu_data structure's ->deferred_qs field is used to indicate that the current CPU is blocking an expedited grace period (perhaps a future one). Given that it is used only for expedited grace periods, its current name is misleading, so this commit renames it to ->exp_deferred_qs. Signed-off-by: Paul E. McKenney

rcu: Avoid self-IPI in sync_sched_exp_online_cleanup()

2019-05-25T21:50:50Z

The sync_sched_exp_online_cleanup() is invoked at online time to handle the case where the start of an expedited grace period ran concurrently with a CPU being taken offline and then immediately being placed online. It checks to see if RCU needs an expedited quiescent state from the incoming CPU, sending it an IPI if so. However, it is quite possible that sync_sched_exp_online_cleanup() is running on that CPU, in which case it is considerably less overhead to simply request the quiescent state locally instead of simulating a self-IPI. This commit therefore places the last few lines of rcu_exp_handler() into a new rcu_exp_need_qs() function, which is invoked both by rcu_exp_handler() and by sync_sched_exp_online_cleanup() in the self-IPI case. This also reduces the rcu_exp_handler() function's state space by removing the direct call that this smp_call_function_single() uses to emulate the requested self-IPI. This in turn will allow tighter error checking in rcu_is_cpu_rrupt_from_idle(). Signed-off-by: Paul E. McKenney Reviewed-by: Joel Fernandes (Google)

rcu: Avoid self-IPI in sync_rcu_exp_select_node_cpus()

2019-05-25T21:50:50Z

Although sync_rcu_exp_select_node_cpus() treats the current CPU as being in a quiescent state, it might well migrate to some other CPU before reaching the smp_call_function_single(), which could then result in an unnecessary simulated self-IPI. This commit therefore instead simply refuses to invoke smp_call_function_single() on the current CPU, which causes the later rcu_report_exp_cpu_mult() to report this CPU's quiescent state with less overhead. This also reduces the rcu_exp_handler() function's state space by removing the direct call that this smp_call_function_single() uses to emulate the requested self-IPI. Signed-off-by: Paul E. McKenney [ paulmck: Use get_cpu() instead of preempt_disable() per Joel Fernandes. ]

Merge branches 'consolidate.2019.04.09a', 'doc.2019.03.26b', 'fixes.2019.03.26b', 'srcu.2019.03.26b', 'stall.2019.03.26b' and 'torture.2019.03.26b' into HEAD

2019-04-09T15:08:13Z

consolidate.2019.04.09a: Lingering RCU flavor consolidation cleanups. doc.2019.03.26b: Documentation updates. fixes.2019.03.26b: Miscellaneous fixes. srcu.2019.03.26b: SRCU updates. stall.2019.03.26b: RCU CPU stall warning updates. torture.2019.03.26b: Torture-test updates.

rcu: Move rcu_print_task_exp_stall() to tree_exp.h

2019-03-26T21:40:13Z

Because expedited CPU stall warnings are contained within the kernel/rcu/tree_exp.h file, rcu_print_task_exp_stall() should live there too. This commit carries out the required code motion. Signed-off-by: Paul E. McKenney

rcu: Correct READ_ONCE()/WRITE_ONCE() for ->rcu_read_unlock_special

2019-03-26T21:38:38Z

The task_struct structure's ->rcu_read_unlock_special field is only ever read or written by the owning task, but it is accessed both at process and interrupt levels. It may therefore be accessed using plain reads and writes while interrupts are disabled, but must be accessed using READ_ONCE() and WRITE_ONCE() or better otherwise. This commit makes a few adjustments to align with this discipline. Signed-off-by: Paul E. McKenney