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srcu: Add notrace variant of srcu_dereference 

In the last patch in this series, we are making lockdep register hooks
onto the irq_{disable,enable} tracepoints. These tracepoints use the
_rcuidle tracepoint variant. In this series we switch the _rcuidle
tracepoint callers to use SRCU instead of sched-RCU. Inorder to
dereference the pointer to the probe functions, we could call
srcu_dereference, however this API will call back into lockdep to check
if the lock is held *before* the lockdep probe hooks have a chance to
run and annotate the IRQ enabled/disabled state.

For this reason we need a notrace variant of srcu_dereference since
otherwise we get lockdep splats. This patch adds the needed
srcu_dereference_notrace variant.

Link: http://lkml.kernel.org/r/20180628182149.226164-3-joel@joelfernandes.org

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Joel Fernandes (Google) 2018-06-28 11:21:44 -07:00 committed by Steven Rostedt (VMware)
parent 1f45a4db36
commit 0b764a6e4e
1 changed files with 5 additions and 0 deletions
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5
include/linux/srcu.h
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@ -169,6 +169,11 @@ static inline int srcu_read_lock_held(const struct srcu_struct *sp)
*/
#define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
/**
* srcu_dereference_notrace - no tracing and no lockdep calls from here
*/
#define srcu_dereference_notrace(p, sp) srcu_dereference_check((p), (sp), 1)
/**
* srcu_read_lock - register a new reader for an SRCU-protected structure.
* @sp: srcu_struct in which to register the new reader.