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

Since commit d9a3da0699 ("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: Boqun Feng <boqun.feng@gmail.com>
Fixes: d9a3da0699 ("rcu: Add expedited grace-period support for preemptible RCU")
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
This commit is contained in:
Boqun Feng 2018-03-07 16:49:39 +08:00 committed by Paul E. McKenney
parent 25f3d7effa
commit 7be8c56f8f
1 changed files with 3 additions and 7 deletions
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10
kernel/rcu/tree_exp.h
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@ -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 * for the current expedited grace period. Works only for preemptible
* RCU -- other RCU implementation use other means. * 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) 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 * recursively up the tree. (Calm down, calm down, we do the recursion
* iteratively!) * iteratively!)
* *
* Caller must hold the rcu_state's exp_mutex and the specified rcu_node * Caller must hold the specified rcu_node structure's ->lock.
* structure's ->lock.
*/ */
static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
bool wake, unsigned long flags) 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 * Report expedited quiescent state for specified node. This is a
* lock-acquisition wrapper function for __rcu_report_exp_rnp(). * 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, static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,
struct rcu_node *rnp, bool wake) 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 * Report expedited quiescent state for multiple CPUs, all covered by the
* specified leaf rcu_node structure. Caller must hold the rcu_state's * specified leaf rcu_node structure.
* exp_mutex.
*/ */
static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp, static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp,
unsigned long mask, bool wake) unsigned long mask, bool wake)