wireguard-linux/kernel/rcu/tree_exp.h, branch jd/unified-crypt-queue

Merge branches 'doc.2020.02.27a', 'fixes.2020.03.21a', 'kfree_rcu.2020.02.20a', 'locktorture.2020.02.20a', 'ovld.2020.02.20a', 'rcu-tasks.2020.02.20a', 'srcu.2020.02.20a' and 'torture.2020.02.20a' into HEAD

2020-03-22T00:15:11Z

doc.2020.02.27a: Documentation updates. fixes.2020.03.21a: Miscellaneous fixes. kfree_rcu.2020.02.20a: Updates to kfree_rcu(). locktorture.2020.02.20a: Lock torture-test updates. ovld.2020.02.20a: Updates to callback-overload handling. rcu-tasks.2020.02.20a: RCU-tasks updates. srcu.2020.02.20a: SRCU updates. torture.2020.02.20a: Torture-test updates.

rcutorture: Allow boottime stall warnings to be suppressed

2020-02-21T00:03:30Z

In normal production, an RCU CPU stall warning at boottime is often just as bad as at any other time. In fact, given the desire for fast boot, any sort of long-term stall at boot is a bad idea. However, heavy rcutorture testing on large hyperthreaded systems can generate boottime RCU CPU stalls as a matter of course. This commit therefore provides a kernel boot parameter that suppresses reporting of boottime RCU CPU stall warnings and similarly of rcutorture writer stalls. Signed-off-by: Paul E. McKenney

rcutorture: Suppress forward-progress complaints during early boot

2020-02-21T00:03:30Z

Some larger systems can take in excess of 50 seconds to complete their early boot initcalls prior to spawing init. This does not in any way help the forward-progress judgments of built-in rcutorture (when rcutorture is built as a module, the insmod or modprobe command normally cannot happen until some time after boot completes). This commit therefore suppresses such complaints until about the time that init is spawned. This also includes a fix to a stupid error located by kbuild test robot. [ paulmck: Apply kbuild test robot feedback. ] Signed-off-by: Paul E. McKenney [ paulmck: Fix to nohz_full slow-expediting recovery logic, per bpetkov. ] [ paulmck: Restrict splat to CONFIG_PREEMPT_RT=y kernels and simplify. ] Tested-by: Borislav Petkov

rcu: Add WRITE_ONCE to rcu_node ->exp_seq_rq store

2020-02-20T23:58:22Z

The rcu_node structure's ->exp_seq_rq field is read locklessly, so this commit adds the WRITE_ONCE() to a load in order to provide proper documentation and READ_ONCE()/WRITE_ONCE() pairing. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney

rcu: Fix exp_funnel_lock()/rcu_exp_wait_wake() datarace

2020-02-20T23:58:21Z

The rcu_node structure's ->exp_seq_rq field is accessed locklessly, so updates must use WRITE_ONCE(). This commit therefore adds the needed WRITE_ONCE() invocation where it was missed. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney

rcu: Forgive slow expedited grace periods at boot time

2020-01-25T20:00:40Z

Boot-time processing often loops in the kernel longer than one might prefer, which can prevent expedited grace periods from completing in a timely manner. This in turn triggers a splat In nohz_full CPUs One could argue that long-looping code should be fixed, but on the other hand, boot time is a bit special. This commit therefore removes the splat. Later commits will add the splat back in, but in a way that removes false positives. Reported-by: Borislav Petkov Signed-off-by: Paul E. McKenney

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: Provide wrappers for uses of ->rcu_read_lock_nesting

2020-01-24T18:27:33Z

This commit provides wrapper functions for uses of ->rcu_read_lock_nesting to improve readability and to ease future changes to support inlining of __rcu_read_lock() and __rcu_read_unlock(). Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney

rcu: Use CONFIG_PREEMPTION where appropriate

2019-12-09T20:37:51Z

The config option `CONFIG_PREEMPT' is used for the preemption model "Low-Latency Desktop". The config option `CONFIG_PREEMPTION' is enabled when kernel preemption is enabled which is true for the preemption model `CONFIG_PREEMPT' and `CONFIG_PREEMPT_RT'. Use `CONFIG_PREEMPTION' if it applies to both preemption models and not just to `CONFIG_PREEMPT'. Cc: "Paul E. McKenney" Cc: Josh Triplett Cc: Steven Rostedt Cc: Mathieu Desnoyers Cc: Lai Jiangshan Cc: Joel Fernandes Cc: Davidlohr Bueso Cc: rcu@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Paul E. McKenney

rcu: Enable tick for nohz_full CPUs slow to provide expedited QS

2019-12-09T20:32:59Z

An expedited grace period can be stalled by a nohz_full CPU looping in kernel context. This possibility is currently handled by some carefully crafted checks in rcu_read_unlock_special() that enlist help from ksoftirqd when permitted by the scheduler. However, it is exactly these checks that require the scheduler avoid holding any of its rq or pi locks across rcu_read_unlock() without also having held them across the entire RCU read-side critical section. It would therefore be very nice if expedited grace periods could handle nohz_full CPUs looping in kernel context without such checks. This commit therefore adds code to the expedited grace period's wait and cleanup code that forces the scheduler-clock interrupt on for CPUs that fail to quickly supply a quiescent state. "Quickly" is currently a hard-coded single-jiffy delay. Signed-off-by: Paul E. McKenney