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Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Browse source 
Pull RCU changes from Ingo Molnar:
 "SRCU changes:

   - These include debugging aids, updates that move towards the goal of
     permitting srcu_read_lock() and srcu_read_unlock() to be used from
     idle and offline CPUs, and a few small fixes.

  Changes to rcutorture and to RCU documentation:

   - Posted to LKML at https://lkml.org/lkml/2013/1/26/188

  Enhancements to uniprocessor handling in tiny RCU:

   - Posted to LKML at https://lkml.org/lkml/2013/1/27/2

  Tag RCU callbacks with grace-period number to simplify callback
  advancement:

   - Posted to LKML at https://lkml.org/lkml/2013/1/26/203

  Miscellaneous fixes:

   - Posted to LKML at https://lkml.org/lkml/2013/1/26/204"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
  srcu: use ACCESS_ONCE() to access sp->completed in srcu_read_lock()
  srcu: Update synchronize_srcu_expedited()'s comments
  srcu: Update synchronize_srcu()'s comments
  srcu: Remove checks preventing idle CPUs from calling srcu_read_lock()
  srcu: Remove checks preventing offline CPUs from calling srcu_read_lock()
  srcu: Simple cleanup for cleanup_srcu_struct()
  srcu: Add might_sleep() annotation to synchronize_srcu()
  srcu: Simplify __srcu_read_unlock() via this_cpu_dec()
  rcu: Allow rcutorture to be built at low optimization levels
  rcu: Make rcutorture's shuffler task shuffle recently added tasks
  rcu: Allow TREE_PREEMPT_RCU on UP systems
  rcu: Provide RCU CPU stall warnings for tiny RCU
  context_tracking: Add comments on interface and internals
  rcu: Remove obsolete Kconfig option from comment
  rcu: Remove unused code originally used for context tracking
  rcu: Consolidate debugging Kconfig options
  rcu: Correct 'optimized' to 'optimize' in header comment
  rcu: Trace callback acceleration
  rcu: Tag callback lists with corresponding grace-period number
  rcutorture: Don't compare ptr with 0
  ...
This commit is contained in:
Linus Torvalds 2013-02-19 17:45:20 -08:00
commit e84cf5d0fd
17 changed files with 556 additions and 229 deletions
Download patch file Download diff file Expand all files Collapse all files

15
include/linux/rcupdate.h
View file

@ -53,7 +53,10 @@ extern int rcutorture_runnable; /* for sysctl */
extern void rcutorture_record_test_transition(void);
extern void rcutorture_record_progress(unsigned long vernum);
extern void do_trace_rcu_torture_read(char *rcutorturename,
struct rcu_head *rhp);
struct rcu_head *rhp,
unsigned long secs,
unsigned long c_old,
unsigned long c);
#else
static inline void rcutorture_record_test_transition(void)
{
@ -63,9 +66,13 @@ static inline void rcutorture_record_progress(unsigned long vernum)
}
#ifdef CONFIG_RCU_TRACE
extern void do_trace_rcu_torture_read(char *rcutorturename,
struct rcu_head *rhp);
struct rcu_head *rhp,
unsigned long secs,
unsigned long c_old,
unsigned long c);
#else
#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
do { } while (0)
#endif
#endif
@ -749,7 +756,7 @@ static inline void rcu_preempt_sleep_check(void)
* preemptible RCU implementations (TREE_PREEMPT_RCU and TINY_PREEMPT_RCU)
* in CONFIG_PREEMPT kernel builds, RCU read-side critical sections may
* be preempted, but explicit blocking is illegal. Finally, in preemptible
* RCU implementations in real-time (CONFIG_PREEMPT_RT) kernel builds,
* RCU implementations in real-time (with -rt patchset) kernel builds,
* RCU read-side critical sections may be preempted and they may also
* block, but only when acquiring spinlocks that are subject to priority
* inheritance.

26
include/linux/srcu.h
View file

@ -151,30 +151,14 @@ void srcu_barrier(struct srcu_struct *sp);
* Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
* and while lockdep is disabled.
*
* Note that if the CPU is in the idle loop from an RCU point of view
* (ie: that we are in the section between rcu_idle_enter() and
* rcu_idle_exit()) then srcu_read_lock_held() returns false even if
* the CPU did an srcu_read_lock(). The reason for this is that RCU
* ignores CPUs that are in such a section, considering these as in
* extended quiescent state, so such a CPU is effectively never in an
* RCU read-side critical section regardless of what RCU primitives it
* invokes. This state of affairs is required --- we need to keep an
* RCU-free window in idle where the CPU may possibly enter into low
* power mode. This way we can notice an extended quiescent state to
* other CPUs that started a grace period. Otherwise we would delay any
* grace period as long as we run in the idle task.
*
* Similarly, we avoid claiming an SRCU read lock held if the current
* CPU is offline.
* Note that SRCU is based on its own statemachine and it doesn't
* relies on normal RCU, it can be called from the CPU which
* is in the idle loop from an RCU point of view or offline.
*/
static inline int srcu_read_lock_held(struct srcu_struct *sp)
{
if (!debug_lockdep_rcu_enabled())
return 1;
if (rcu_is_cpu_idle())
return 0;
if (!rcu_lockdep_current_cpu_online())
return 0;
return lock_is_held(&sp->dep_map);
}
@ -236,8 +220,6 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
int retval = __srcu_read_lock(sp);
rcu_lock_acquire(&(sp)->dep_map);
rcu_lockdep_assert(!rcu_is_cpu_idle(),
"srcu_read_lock() used illegally while idle");
return retval;
}
@ -251,8 +233,6 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
__releases(sp)
{
rcu_lockdep_assert(!rcu_is_cpu_idle(),
"srcu_read_unlock() used illegally while idle");
rcu_lock_release(&(sp)->dep_map);
__srcu_read_unlock(sp, idx);
}