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-rw-r--r--include/linux/srcu.h26
1 files changed, 3 insertions, 23 deletions
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 6eb691b08358..04f4121a23ae 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -151,30 +151,14 @@ void srcu_barrier(struct srcu_struct *sp);
151 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot 151 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
152 * and while lockdep is disabled. 152 * and while lockdep is disabled.
153 * 153 *
154 * Note that if the CPU is in the idle loop from an RCU point of view 154 * Note that SRCU is based on its own statemachine and it doesn't
155 * (ie: that we are in the section between rcu_idle_enter() and 155 * relies on normal RCU, it can be called from the CPU which
156 * rcu_idle_exit()) then srcu_read_lock_held() returns false even if 156 * is in the idle loop from an RCU point of view or offline.
157 * the CPU did an srcu_read_lock(). The reason for this is that RCU
158 * ignores CPUs that are in such a section, considering these as in
159 * extended quiescent state, so such a CPU is effectively never in an
160 * RCU read-side critical section regardless of what RCU primitives it
161 * invokes. This state of affairs is required --- we need to keep an
162 * RCU-free window in idle where the CPU may possibly enter into low
163 * power mode. This way we can notice an extended quiescent state to
164 * other CPUs that started a grace period. Otherwise we would delay any
165 * grace period as long as we run in the idle task.
166 *
167 * Similarly, we avoid claiming an SRCU read lock held if the current
168 * CPU is offline.
169 */ 157 */
170static inline int srcu_read_lock_held(struct srcu_struct *sp) 158static inline int srcu_read_lock_held(struct srcu_struct *sp)
171{ 159{
172 if (!debug_lockdep_rcu_enabled()) 160 if (!debug_lockdep_rcu_enabled())
173 return 1; 161 return 1;
174 if (rcu_is_cpu_idle())
175 return 0;
176 if (!rcu_lockdep_current_cpu_online())
177 return 0;
178 return lock_is_held(&sp->dep_map); 162 return lock_is_held(&sp->dep_map);
179} 163}
180 164
@@ -236,8 +220,6 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
236 int retval = __srcu_read_lock(sp); 220 int retval = __srcu_read_lock(sp);
237 221
238 rcu_lock_acquire(&(sp)->dep_map); 222 rcu_lock_acquire(&(sp)->dep_map);
239 rcu_lockdep_assert(!rcu_is_cpu_idle(),
240 "srcu_read_lock() used illegally while idle");
241 return retval; 223 return retval;
242} 224}
243 225
@@ -251,8 +233,6 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
251static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) 233static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
252 __releases(sp) 234 __releases(sp)
253{ 235{
254 rcu_lockdep_assert(!rcu_is_cpu_idle(),
255 "srcu_read_unlock() used illegally while idle");
256 rcu_lock_release(&(sp)->dep_map); 236 rcu_lock_release(&(sp)->dep_map);
257 __srcu_read_unlock(sp, idx); 237 __srcu_read_unlock(sp, idx);
258} 238}