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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-02-23 04:04:45 +0300
committerIngo Molnar <mingo@elte.hu>2010-02-25 11:40:59 +0300
commit632ee200130899252508c478ad0e808222573fbc (patch)
treee3f44ca9daf2a2da2186419f703bc9cec8faa058 /lib
parent996de8c6fe95c5a9fc524241cc8f142ef0605d3d (diff)
downloadlinux-632ee200130899252508c478ad0e808222573fbc.tar.xz
rcu: Introduce lockdep-based checking to RCU read-side primitives
Inspection is proving insufficient to catch all RCU misuses, which is understandable given that rcu_dereference() might be protected by any of four different flavors of RCU (RCU, RCU-bh, RCU-sched, and SRCU), and might also/instead be protected by any of a number of locking primitives. It is therefore time to enlist the aid of lockdep. This set of patches is inspired by earlier work by Peter Zijlstra and Thomas Gleixner, and takes the following approach: o Set up separate lockdep classes for RCU, RCU-bh, and RCU-sched. o Set up separate lockdep classes for each instance of SRCU. o Create primitives that check for being in an RCU read-side critical section. These return exact answers if lockdep is fully enabled, but if unsure, report being in an RCU read-side critical section. (We want to avoid false positives!) The primitives are: For RCU: rcu_read_lock_held(void) For RCU-bh: rcu_read_lock_bh_held(void) For RCU-sched: rcu_read_lock_sched_held(void) For SRCU: srcu_read_lock_held(struct srcu_struct *sp) o Add rcu_dereference_check(), which takes a second argument in which one places a boolean expression based on the above primitives and/or lockdep_is_held(). o A new kernel configuration parameter, CONFIG_PROVE_RCU, enables rcu_dereference_check(). This depends on CONFIG_PROVE_LOCKING, and should be quite helpful during the transition period while CONFIG_PROVE_RCU-unaware patches are in flight. The existing rcu_dereference() primitive does no checking, but upcoming patches will change that. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1266887105-1528-1-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.debug12
-rw-r--r--lib/debug_locks.c1
2 files changed, 13 insertions, 0 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 6bf97d176326..6af20a8a0a54 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -499,6 +499,18 @@ config PROVE_LOCKING
For more details, see Documentation/lockdep-design.txt.
+config PROVE_RCU
+ bool "RCU debugging: prove RCU correctness"
+ depends on PROVE_LOCKING
+ default n
+ help
+ This feature enables lockdep extensions that check for correct
+ use of RCU APIs. This is currently under development. Say Y
+ if you want to debug RCU usage or help work on the PROVE_RCU
+ feature.
+
+ Say N if you are unsure.
+
config LOCKDEP
bool
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
diff --git a/lib/debug_locks.c b/lib/debug_locks.c
index bc3b11731b9c..5bf0020b9248 100644
--- a/lib/debug_locks.c
+++ b/lib/debug_locks.c
@@ -23,6 +23,7 @@
* shut up after that.
*/
int debug_locks = 1;
+EXPORT_SYMBOL_GPL(debug_locks);
/*
* The locking-testsuite uses <debug_locks_silent> to get a