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Commit 7be8c56f authored by Boqun Feng's avatar Boqun Feng Committed by Paul E. McKenney
Browse files

rcu: exp: Fix "must hold exp_mutex" comments for QS reporting functions 



Since commit d9a3da06 ("rcu: Add expedited grace-period support
for preemptible RCU"), there are comments for some funtions in
rcu_report_exp_rnp()'s call-chain saying that exp_mutex or its
predecessors needs to be held.

However, exp_mutex and its predecessors were used only to synchronize
between GPs, and it is clear that all variables visited by those functions
are under the protection of rcu_node's ->lock. Moreover, those functions
are currently called without held exp_mutex, and seems that doesn't
introduce any trouble.

So this patch fixes this problem by updating the comments to match the
current code.

Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Fixes: d9a3da06 ("rcu: Add expedited grace-period support for preemptible RCU")
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: default avatarNicholas Piggin <npiggin@gmail.com>
parent 25f3d7ef

kernel/rcu/tree_exp.h

+3 −7
Original line number Diff line number Diff line
@@ -154,7 +154,7 @@ static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp) 
 * for the current expedited grace period.  Works only for preemptible

 * RCU -- other RCU implementation use other means.

 *

 * Caller must hold the rcu_state's exp_mutex.

 * Caller must hold the specificed rcu_node structure's ->lock

 */

static bool sync_rcu_preempt_exp_done(struct rcu_node *rnp)

{
@@ -170,8 +170,7 @@ static bool sync_rcu_preempt_exp_done(struct rcu_node *rnp) 
 * recursively up the tree.  (Calm down, calm down, we do the recursion

 * iteratively!)

 *

 * Caller must hold the rcu_state's exp_mutex and the specified rcu_node

 * structure's ->lock.

 * Caller must hold the specified rcu_node structure's ->lock.

 */

static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,

				 bool wake, unsigned long flags)
@@ -207,8 +206,6 @@ static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, 
/*

 * Report expedited quiescent state for specified node.  This is a

 * lock-acquisition wrapper function for __rcu_report_exp_rnp().

 *

 * Caller must hold the rcu_state's exp_mutex.

 */

static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,

					      struct rcu_node *rnp, bool wake)
@@ -221,8 +218,7 @@ static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp, 


/*

 * Report expedited quiescent state for multiple CPUs, all covered by the

 * specified leaf rcu_node structure.  Caller must hold the rcu_state's

 * exp_mutex.

 * specified leaf rcu_node structure.

 */

static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp,

				    unsigned long mask, bool wake)