linux/kernel/torture.c, branch v5.1

Merge branches 'doc.2019.01.26a', 'fixes.2019.01.26a', 'sil.2019.01.26a', 'spdx.2019.02.09a', 'srcu.2019.01.26a' and 'torture.2019.01.26a' into HEAD

2019-02-09T16:47:52Z

doc.2019.01.26a: Documentation updates. fixes.2019.01.26a: Miscellaneous fixes. sil.2019.01.26a: Removal of a few more spin_is_locked() instances. spdx.2019.02.09a: Add SPDX identifiers to RCU files srcu.2019.01.26a: SRCU updates. torture.2019.01.26a: Torture-test updates.

torture: Convert to SPDX license identifier

2019-02-09T16:46:10Z

Replace the license boiler plate with a SPDX license identifier. While in the area, update an email address. Signed-off-by: Paul E. McKenney Reviewed-by: Thomas Gleixner

rcutorture: Add grace period after CPU offline

2019-01-25T23:37:10Z

Beyond a certain point in the CPU-hotplug offline process, timers get stranded on the outgoing CPU, and won't fire until that CPU comes back online, which might well be never. This commit therefore adds a hook in torture_onoff_init() that is invoked from torture_offline(), which rcutorture uses to occasionally wait for a grace period. This should result in failures for RCU implementations that rely on stranded timers eventually firing in the absence of the CPU coming back online. Reported-by: Sebastian Andrzej Siewior Signed-off-by: Paul E. McKenney

torture: Remove unnecessary "ret" variables

2018-12-01T20:45:35Z

Remove return variables (declared as "ret") in cases where, depending on whether a condition evaluates as true, the result of a function call can be immediately returned instead of storing the result in the return variable. When the condition evaluates as false, the constant initially stored in the return variable at declaration is returned instead. Signed-off-by: Pierce Griffiths Signed-off-by: Paul E. McKenney

torture: Bring any extra CPUs online during kernel startup

2018-12-01T20:45:32Z

Currently, the torture scripts rely on the initrd/init script to bring any extra CPUs online, for example, in the case where the kernel and qemu have different ideas about how many CPUs are present. This works, but is an unnecessary dependency on initrd, which needs to vary depending on the distro. This commit therefore causes torture_onoff() to check for additional CPUs, attempting to bring any found online. Errors are ignored, just as they are by the initrd/init script. Signed-off-by: Paul E. McKenney

rcutorture: Check GP completion at stutter end

2018-08-29T16:20:48Z

The rcu_torture_writer() function invokes stutter_wait() at the end of each writer pass, which occasionally blocks for an extended time period in order to ensure that RCU can handle intermittent loads. But part of handling a busy period is invoking all the callbacks before the end of the idle period induced by stutter_wait(). This commit therefore adds a return value to stutter_wait() indicating whether stutter_wait() actually waited. In addition, this commit causes rcu_torture_writer() to test this value and if set, checks that all the elements of the rcu_tortures[] array have been freed up. Signed-off-by: Paul E. McKenney

torture: Keep old-school dmesg format

2018-06-25T18:30:10Z

This commit adds "#define pr_fmt(fmt) fmt" to the torture-test files in order to keep the current dmesg format. Once Joe's commits have hit mainline, these definitions will be changed in order to automatically generate the dmesg line prefix that the scripts expect. This will have the beneficial side-effect of allowing printk() formats to be used more widely and of shortening some pr_*() lines. Signed-off-by: Paul E. McKenney Cc: Joe Perches

torture: Make online/offline messages appear only for verbose=2

2018-06-25T18:30:10Z

Some bugs reproduce quickly only at high CPU-hotplug rates, so the rcutorture TREE03 scenario now has only 200 milliseconds spacing between CPU-hotplug operations. At this rate, the torture-test pair of console messages per operation becomes a bit voluminous. This commit therefore converts the torture-test set of "verbose" kernel-boot arguments from bool to int, and prints the extra console messages only when verbose=2. The default is still verbose=1. Signed-off-by: Paul E. McKenney

rcu: Rename cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs()

2018-05-15T17:27:29Z

Commit e31d28b6ab8f ("trace: Eliminate cond_resched_rcu_qs() in favor of cond_resched()") substituted cond_resched() for the earlier call to cond_resched_rcu_qs(). However, the new-age cond_resched() does not do anything to help RCU-tasks grace periods because (1) RCU-tasks is only enabled when CONFIG_PREEMPT=y and (2) cond_resched() is a complete no-op when preemption is enabled. This situation results in hangs when running the trace benchmarks. A number of potential fixes were discussed on LKML (https://lkml.kernel.org/r/20180224151240.0d63a059@vmware.local.home), including making cond_resched() not be a no-op; making cond_resched() not be a no-op, but only when running tracing benchmarks; reverting the aforementioned commit (which works because cond_resched_rcu_qs() does provide an RCU-tasks quiescent state; and adding a call to the scheduler/RCU rcu_note_voluntary_context_switch() function. All were deemed unsatisfactory, either due to added cond_resched() overhead or due to magic functions inviting cargo culting. This commit renames cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs(), which provides a clear hint as to what this function is doing and why and where it should be used, and then replaces the call to cond_resched() with cond_resched_tasks_rcu_qs() in the trace benchmark's benchmark_event_kthread() function. Reported-by: Steven Rostedt Signed-off-by: Paul E. McKenney Tested-by: Nicholas Piggin

torture: Save a line in stutter_wait(): while -> for

2017-12-11T17:18:30Z

Signed-off-by: Paul E. McKenney