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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-02-22 20:04:45 -0500
committerIngo Molnar <mingo@elte.hu>2010-02-25 03:40:59 -0500
commit632ee200130899252508c478ad0e808222573fbc (patch)
treee3f44ca9daf2a2da2186419f703bc9cec8faa058 /kernel/rcutorture.c
parent996de8c6fe95c5a9fc524241cc8f142ef0605d3d (diff)
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 'kernel/rcutorture.c')
-rw-r--r--kernel/rcutorture.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index adda92bfafac..5f43f30fcd1d 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -796,7 +796,11 @@ static void rcu_torture_timer(unsigned long unused)
796 796
797 idx = cur_ops->readlock(); 797 idx = cur_ops->readlock();
798 completed = cur_ops->completed(); 798 completed = cur_ops->completed();
799 p = rcu_dereference(rcu_torture_current); 799 p = rcu_dereference_check(rcu_torture_current,
800 rcu_read_lock_held() ||
801 rcu_read_lock_bh_held() ||
802 rcu_read_lock_sched_held() ||
803 srcu_read_lock_held(&srcu_ctl));
800 if (p == NULL) { 804 if (p == NULL) {
801 /* Leave because rcu_torture_writer is not yet underway */ 805 /* Leave because rcu_torture_writer is not yet underway */
802 cur_ops->readunlock(idx); 806 cur_ops->readunlock(idx);
@@ -853,7 +857,11 @@ rcu_torture_reader(void *arg)
853 } 857 }
854 idx = cur_ops->readlock(); 858 idx = cur_ops->readlock();
855 completed = cur_ops->completed(); 859 completed = cur_ops->completed();
856 p = rcu_dereference(rcu_torture_current); 860 p = rcu_dereference_check(rcu_torture_current,
861 rcu_read_lock_held() ||
862 rcu_read_lock_bh_held() ||
863 rcu_read_lock_sched_held() ||
864 srcu_read_lock_held(&srcu_ctl));
857 if (p == NULL) { 865 if (p == NULL) {
858 /* Wait for rcu_torture_writer to get underway */ 866 /* Wait for rcu_torture_writer to get underway */
859 cur_ops->readunlock(idx); 867 cur_ops->readunlock(idx);