diff options
| author | Paul E. McKenney <paulmck@kernel.org> | 2020-08-05 15:51:20 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-08-24 18:40:23 -0700 |
| commit | 8cbd0e38a9f2de38e8991c5c1c6f9024b2731d17 (patch) | |
| tree | 76783dac4e2eb416433c323cb967ddc7b4e7305f /kernel/rcu/Kconfig.debug | |
| parent | 9123e3a74ec7b934a4a099e98af6a61c2f80bbf5 (diff) | |
rcu: Add Kconfig option for strict RCU grace periods
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>
Diffstat (limited to 'kernel/rcu/Kconfig.debug')
| -rw-r--r-- | kernel/rcu/Kconfig.debug | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug index 3cf6132a4bb9..cab5a4bebe9c 100644 --- a/kernel/rcu/Kconfig.debug +++ b/kernel/rcu/Kconfig.debug @@ -114,4 +114,19 @@ config RCU_EQS_DEBUG Say N here if you need ultimate kernel/user switch latencies Say Y if you are unsure +config RCU_STRICT_GRACE_PERIOD + bool "Provide debug RCU implementation with short grace periods" + depends on DEBUG_KERNEL && RCU_EXPERT + default n + select PREEMPT_COUNT if PREEMPT=n + help + Select this option to build an RCU variant that is strict about + grace periods, making them as short as it can. This limits + scalability, destroys real-time response, degrades battery + lifetime and kills performance. Don't try this on large + machines, as in systems with more than about 10 or 20 CPUs. + But in conjunction with tools like KASAN, it can be helpful + when looking for certain types of RCU usage bugs, for example, + too-short RCU read-side critical sections. + endmenu # "RCU Debugging" |