user/sven/linux.git/kernel/scftorture.c, branch v5.15.55

scftorture: Fix distribution of short handler delays

2022-06-09T08:22:46Z

[ Upstream commit 8106bddbab5f0ba180e6d693c7c1fc6926d57caa ] The scftorture test module's scf_handler() function is supposed to provide three different distributions of short delays (including "no delay") and one distribution of long delays, if specified by the scftorture.longwait module parameter. However, the second of the two non-zero-wait short delays is disabled due to the first such delay's "goto out" not being enclosed in the "then" clause with the "udelay()". This commit therefore adjusts the code to provide the intended set of delays. Fixes: e9d338a0b179 ("scftorture: Add smp_call_function() torture test") Signed-off-by: Paul E. McKenney Signed-off-by: Sasha Levin

scftorture: Avoid NULL pointer exception on early exit

2021-07-27T18:39:30Z

When scftorture finds an error in the module parameters controlling the relative frequencies of smp_call_function*() variants, it takes an early exit. So early that it has not allocated memory to track the kthreads running the test, which results in a segfault. This commit therefore checks for the existence of the memory before attempting to stop the kthreads that would otherwise have been recorded in that non-existent memory. Signed-off-by: Paul E. McKenney

scftorture: Add RPC-like IPI tests

2021-07-27T18:39:30Z

This commit adds the single_weight_rpc module parameter, which causes the IPI handler to awaken the IPI sender. In many scheduler configurations, this will result in an IPI back to the sender that is likely to be received at a time when the sender CPU is idle. The intent is to stress IPI reception during CPU busy-to-idle transitions. Signed-off-by: Paul E. McKenney

scftorture: Avoid false-positive warnings in scftorture_invoker()

2021-07-06T19:37:55Z

If the call to set_cpus_allowed_ptr() in scftorture_invoker() fails, a later WARN_ONCE() complains. But with the advent of 570a752b7a9b ("lib/smp_processor_id: Use is_percpu_thread() instead of nr_cpus_allowed"), this complaint can be drowned out by complaints from smp_processor_id(). The rationale for this change is that scftorture's kthreads are not marked with PF_NO_SETAFFINITY, which means that a system administrator could change affinity at any time. However, scftorture is a torture test, and the system administrator might well have a valid test-the-test reason for changing affinity. This commit therefore changes to raw_smp_processor_id() in order to avoid the noise, and also adds a WARN_ON_ONCE() to the call to set_cpus_allowed_ptr() in order to directly detect immediate failure. There is no WARN_ON_ONCE() within the test loop, allowing human-reflex-based affinity resetting, if desired. Signed-off-by: Paul E. McKenney

scftorture: Add debug output for wrong-CPU warning

2021-01-04T21:53:41Z

This commit adds the desired CPU, the actual CPU, and nr_cpu_ids to the wrong-CPU warning in scftorture_invoker(), the better to help with debugging. Signed-off-by: Paul E. McKenney

scftorture: Add full-test stutter capability

2020-11-07T01:13:56Z

In virtual environments on systems with hardware assist, inter-processor interrupts must do very different things based on whether the target vCPU is running or not. This commit therefore enables torture-test stuttering to better test these running/not-running transitions. Suggested-by: Chris Mason Signed-off-by: Paul E. McKenney

scftorture: Add an alternative IPI vector

2020-11-07T01:13:49Z

The scftorture tests currently use only smp_call_function() and friends, which means that these tests cannot locate bugs caused by interactions between different IPI vectors. This commit therefore adds the rescheduling IPI to the mix. Note that this commit permits resched_cpus() only when scftorture is built in. This is a workaround. Longer term, this will use real wakeups rather than resched_cpu(). Signed-off-by: Paul E. McKenney

scftorture: Add cond_resched() to test loop

2020-08-25T01:38:38Z

Although the test loop does randomly delay, which would provide quiescent states and so forth, it is possible for there to be a series of long smp_call_function*() handler runtimes with no delays, which results in softlockup and RCU CPU stall warning messages. This commit therefore inserts a cond_resched() into the main test loop. Signed-off-by: Paul E. McKenney

scftorture: Adapt memory-ordering test to UP operation

2020-08-25T01:38:37Z

On uniprocessor systems, smp_call_function() does nothing. This commit therefore avoids complaining about the lack of handler accesses in the single-CPU case where there is no handler. Signed-off-by: Paul E. McKenney

scftorture: Block scftorture_invoker() kthreads for offline CPUs

2020-08-25T01:38:37Z

Currently, CPU-hotplug operations might result in all but two of (say) 100 CPUs being offline, which in turn might result in false-positive diagnostics due to overload. This commit therefore causes scftorture_invoker() kthreads for offline CPUs to loop blocking for 200 milliseconds at a time, thus continuously adjusting the number of threads to match the number of online CPUs. Signed-off-by: Paul E. McKenney