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| author |  Paul E. McKenney <paulmck@kernel.org>
| 2024-03-07 15:01:54 -0800 |
|---|---|---|
| committer |  Uladzislau Rezki (Sony) <urezki@gmail.com>
| 2024-04-15 13:07:14 +0200 |
| commit | 62bb24c4b022b9ba9cf2e4a72f6cd8c3086f0cf8 (patch) | |
| tree | 3e860e809c6d94bb8370b19c0d140bd251bf12d6 /kernel/rcu | |
| parent | rcu: Make Tiny RCU explicitly disable preemption (diff) | |
| download | linux-62bb24c4b022b9ba9cf2e4a72f6cd8c3086f0cf8.tar.gz linux-62bb24c4b022b9ba9cf2e4a72f6cd8c3086f0cf8.tar.bz2 linux-62bb24c4b022b9ba9cf2e4a72f6cd8c3086f0cf8.zip | |
rcu: Remove redundant READ_ONCE() of rcu_state.gp_flags in tree.c
Although it is functionally OK to do READ_ONCE() of a variable that
cannot change, it is confusing and at best an accident waiting to happen.
This commit therefore removes a number of READ_ONCE(rcu_state.gp_flags)
instances from kernel/rcu/tree.c that are not needed due to updates
to this field being excluded by virtue of holding the root rcu_node
structure's ->lock.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Closes: https://lore.kernel.org/lkml/4857c5ef-bd8f-4670-87ac-0600a1699d05@paulmck-laptop/T/#mccb23c2a4902da4d3c750165329f8de056903c58
Reported-by: Julia Lawall <julia.lawall@inria.fr>
Closes: https://lore.kernel.org/lkml/4857c5ef-bd8f-4670-87ac-0600a1699d05@paulmck-laptop/T/#md1b5c026584f9c3c7b0fbc9240dd7de584597b73
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 11 |
1 files changed, 4 insertions, 7 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 2795a1457acf..559f2d0d271f 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1463,7 +1463,7 @@ static noinline_for_stack bool rcu_gp_init(void) WRITE_ONCE(rcu_state.gp_activity, jiffies); raw_spin_lock_irq_rcu_node(rnp); - if (!READ_ONCE(rcu_state.gp_flags)) { + if (!rcu_state.gp_flags) { /* Spurious wakeup, tell caller to go back to sleep. */ raw_spin_unlock_irq_rcu_node(rnp); return false; @@ -1648,8 +1648,7 @@ static void rcu_gp_fqs(bool first_time) /* Clear flag to prevent immediate re-entry. */ if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) { raw_spin_lock_irq_rcu_node(rnp); - WRITE_ONCE(rcu_state.gp_flags, - READ_ONCE(rcu_state.gp_flags) & ~RCU_GP_FLAG_FQS); + WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags & ~RCU_GP_FLAG_FQS); raw_spin_unlock_irq_rcu_node(rnp); } } @@ -1910,8 +1909,7 @@ static void rcu_report_qs_rsp(unsigned long flags) { raw_lockdep_assert_held_rcu_node(rcu_get_root()); WARN_ON_ONCE(!rcu_gp_in_progress()); - WRITE_ONCE(rcu_state.gp_flags, - READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS); + WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_FQS); raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(), flags); rcu_gp_kthread_wake(); } @@ -2426,8 +2424,7 @@ void rcu_force_quiescent_state(void) raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); return; /* Someone beat us to it. */ } - WRITE_ONCE(rcu_state.gp_flags, - READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS); + WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_FQS); raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); rcu_gp_kthread_wake(); } |