user/sven/linux.git/kernel/scftorture.c, branch v5.10.124

scftorture: Fix distribution of short handler delays

2022-06-09T08:21:01Z

[ 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: 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

scftorture: Check unexpected "switch" statement value

2020-08-25T01:38:37Z

This commit adds a "default" case to the switch statement in scftorture_invoke_one() which contains a WARN_ON_ONCE() and an assignment to ->scfc_out to suppress knock-on warnings. These knock-on warnings could otherwise cause the user to think that there was a memory-ordering problem in smp_call_function() instead of a bug in scftorture.c itself. Signed-off-by: Paul E. McKenney

scftorture: Make symbol 'scf_torture_rand' static

2020-08-25T01:38:36Z

The sparse tool complains as follows kernel/scftorture.c:124:1: warning: symbol '__pcpu_scope_scf_torture_rand' was not declared. Should it be static? And this per-CPU variable is not used outside of scftorture.c, so this commit marks it static. Reported-by: Hulk Robot Signed-off-by: Wei Yongjun Signed-off-by: Paul E. McKenney

scftorture: Prevent compiler from reducing race probabilities

2020-08-25T01:38:36Z

Detecting smp_call_function() memory misordering requires close timing, so it is necessary to have the checks immediately before and after the call to the smp_call_function*() function under test. This commit therefore inserts barrier() calls to prevent the compiler from optimizing memory-misordering detection down into the zone of extreme improbability. Signed-off-by: Paul E. McKenney

scftorture: Flag errors in torture-compatible manner

2020-08-25T01:38:35Z

This commit prints error counts on the statistics line and also adds a "!!!" if any of the counters are non-zero. Allocation failures are (somewhat) forgiven, but all other errors result in a "FAILURE" print at the end of the test. Signed-off-by: Paul E. McKenney

scftorture: Consolidate scftorture_invoke_one() scf_check initialization

2020-08-25T01:38:35Z

This commit hoists much of the initialization of the scf_check structure out of the switch statement, thus saving a few lines of code. The initialization of the ->scfc_in field remains in each leg of the switch statement in order to more heavily stress memory ordering. Signed-off-by: Paul E. McKenney

scftorture: Consolidate scftorture_invoke_one() check and kfree()

2020-08-25T01:38:35Z

This commit moves checking of the ->scfc_out field and the freeing of the scf_check structure down below the end of switch statement, thus saving a few lines of code. Signed-off-by: Paul E. McKenney