strictgp.2020.08.24a: Strict grace periods for KASAN testing.
People running automated tests have asked for a way to make RCU minimize grace-period duration in order to increase the probability of KASAN detecting a pointer being improperly leaked from an RCU read-side critical section, for example, like this: rcu_read_lock(); p = rcu_dereference(gp); do_something_with(p); // OK rcu_read_unlock(); do_something_else_with(p); // BUG!!! The rcupdate.rcu_expedited boot parameter is a start in this direction, given that it makes calls to synchronize_rcu() instead invoke the faster (and more wasteful) synchronize_rcu_expedited(). However, this does nothing to shorten RCU grace periods that are instead initiated by call_rcu(), and RCU pointer-leak bugs can involve call_rcu() just as surely as they can synchronize_rcu(). This commit therefore adds a RCU_STRICT_GRACE_PERIOD Kconfig option that will be used to shorten normal (non-expedited) RCU grace periods. This commit also dumps out a message when this option is in effect. Later commits will actually shorten grace periods. Reported-by Jann Horn <jannh@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit further avoids conflation of rcuperf with the kernel's perf feature by renaming kernel/rcu/rcuperf.c to kernel/rcu/rcuscale.c, and also by similarly renaming the functions and variables inside this file. This has the side effect of changing the names of the kernel boot parameters, so kernel-parameters.txt and ver_functions.sh are also updated. The rcutorture --torture type was also updated from rcuperf to rcuscale. [ paulmck: Fix bugs located by Stephen Rothwell. ] Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The old Kconfig option name is all too easy to conflate with the unrelated "perf" feature, so this commit renames RCU_REF_PERF_TEST to RCU_REF_SCALE_TEST. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Add a test for comparing the performance of RCU with various read-side synchronization mechanisms. The test has proved useful for collecting data and performing these comparisons. Currently RCU, SRCU, reader-writer lock, reader-writer semaphore and reference counting can be measured using refperf.perf_type parameter. Each invocation of the test runs measures performance of a specific mechanism. The maximum number of CPUs to concurrently run readers on is chosen by the test itself and is 75% of the total number of CPUs. So if you had 24 CPUs, the test runs with a maximum of 18 parallel readers. A number of experiments are conducted, and in each experiment, the number of readers is increased by 1, upto the 75% of CPUs mark. During each experiment, all readers execute an empty loop with refperf.loops iterations and time the total loop duration. This is then averaged. Example output: Parameters "refperf.perf_type=srcu refperf.loops=2000000" looks like: [ 3.347133] srcu-ref-perf: [ 3.347133] Threads Time(ns) [ 3.347133] 1 36 [ 3.347133] 2 34 [ 3.347133] 3 34 [ 3.347133] 4 34 [ 3.347133] 5 33 [ 3.347133] 6 33 [ 3.347133] 7 33 [ 3.347133] 8 33 [ 3.347133] 9 33 [ 3.347133] 10 33 [ 3.347133] 11 33 [ 3.347133] 12 33 [ 3.347133] 13 33 [ 3.347133] 14 33 [ 3.347133] 15 32 [ 3.347133] 16 33 [ 3.347133] 17 33 [ 3.347133] 18 34 Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds the definitions required to torture the tracing flavor of RCU tasks. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds the definitions required to torture the rude flavor of RCU tasks. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds RCU-reader checks to list_for_each_entry_rcu() and hlist_for_each_entry_rcu(). These checks are optional, and are indicated by a lockdep expression passed to a new optional argument to these two macros. If this optional lockdep expression is omitted, these two macros act as before, checking for an RCU read-side critical section. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Update to eliminate return within macro and update comment. ] Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Add SPDX license identifiers to all Make/Kconfig files which: - Have no license information of any form These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
RCU's debugging Kconfig options are in the unintuitive location lib/Kconfig.debug, and there are enough of them that it would be good for them to be more centralized. This commit therefore extracts RCU's Kconfig options from init/Kconfig into a new kernel/rcu/Kconfig.debug file. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>