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authorPaul E. McKenney <paulmck@kernel.org>2022-09-15 12:09:30 -0700
committerPaul E. McKenney <paulmck@kernel.org>2022-10-18 11:24:24 -0700
commit5d0f5953b60f5f7a278085b55ddc73e2932f4c33 (patch)
tree1c5dc06211ff365e53b5ccab84f23821dee2da21 /kernel/rcu/srcutree.c
parent9abf2313adc1ca1b6180c508c25f22f9395cc780 (diff)
srcu: Convert ->srcu_lock_count and ->srcu_unlock_count to atomic
NMI-safe variants of srcu_read_lock() and srcu_read_unlock() are needed by printk(), which on many architectures entails read-modify-write atomic operations. This commit prepares Tree SRCU for this change by making both ->srcu_lock_count and ->srcu_unlock_count by atomic_long_t. [ paulmck: Apply feedback from John Ogness. ] Link: https://lore.kernel.org/all/20220910221947.171557773@linutronix.de/ Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: John Ogness <john.ogness@linutronix.de> Cc: Petr Mladek <pmladek@suse.com>
Diffstat (limited to 'kernel/rcu/srcutree.c')
-rw-r--r--kernel/rcu/srcutree.c24
1 files changed, 12 insertions, 12 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 1c304fec89c0..25e9458da6a2 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -417,7 +417,7 @@ static unsigned long srcu_readers_lock_idx(struct srcu_struct *ssp, int idx)
for_each_possible_cpu(cpu) {
struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu);
- sum += READ_ONCE(cpuc->srcu_lock_count[idx]);
+ sum += atomic_long_read(&cpuc->srcu_lock_count[idx]);
}
return sum;
}
@@ -434,7 +434,7 @@ static unsigned long srcu_readers_unlock_idx(struct srcu_struct *ssp, int idx)
for_each_possible_cpu(cpu) {
struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu);
- sum += READ_ONCE(cpuc->srcu_unlock_count[idx]);
+ sum += atomic_long_read(&cpuc->srcu_unlock_count[idx]);
}
return sum;
}
@@ -503,10 +503,10 @@ static bool srcu_readers_active(struct srcu_struct *ssp)
for_each_possible_cpu(cpu) {
struct srcu_data *cpuc = per_cpu_ptr(ssp->sda, cpu);
- sum += READ_ONCE(cpuc->srcu_lock_count[0]);
- sum += READ_ONCE(cpuc->srcu_lock_count[1]);
- sum -= READ_ONCE(cpuc->srcu_unlock_count[0]);
- sum -= READ_ONCE(cpuc->srcu_unlock_count[1]);
+ sum += atomic_long_read(&cpuc->srcu_lock_count[0]);
+ sum += atomic_long_read(&cpuc->srcu_lock_count[1]);
+ sum -= atomic_long_read(&cpuc->srcu_unlock_count[0]);
+ sum -= atomic_long_read(&cpuc->srcu_unlock_count[1]);
}
return sum;
}
@@ -636,7 +636,7 @@ int __srcu_read_lock(struct srcu_struct *ssp)
int idx;
idx = READ_ONCE(ssp->srcu_idx) & 0x1;
- this_cpu_inc(ssp->sda->srcu_lock_count[idx]);
+ this_cpu_inc(ssp->sda->srcu_lock_count[idx].counter);
smp_mb(); /* B */ /* Avoid leaking the critical section. */
return idx;
}
@@ -650,7 +650,7 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock);
void __srcu_read_unlock(struct srcu_struct *ssp, int idx)
{
smp_mb(); /* C */ /* Avoid leaking the critical section. */
- this_cpu_inc(ssp->sda->srcu_unlock_count[idx]);
+ this_cpu_inc(ssp->sda->srcu_unlock_count[idx].counter);
}
EXPORT_SYMBOL_GPL(__srcu_read_unlock);
@@ -1687,8 +1687,8 @@ void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf)
struct srcu_data *sdp;
sdp = per_cpu_ptr(ssp->sda, cpu);
- u0 = data_race(sdp->srcu_unlock_count[!idx]);
- u1 = data_race(sdp->srcu_unlock_count[idx]);
+ u0 = data_race(atomic_long_read(&sdp->srcu_unlock_count[!idx]));
+ u1 = data_race(atomic_long_read(&sdp->srcu_unlock_count[idx]));
/*
* Make sure that a lock is always counted if the corresponding
@@ -1696,8 +1696,8 @@ void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf)
*/
smp_rmb();
- l0 = data_race(sdp->srcu_lock_count[!idx]);
- l1 = data_race(sdp->srcu_lock_count[idx]);
+ l0 = data_race(atomic_long_read(&sdp->srcu_lock_count[!idx]));
+ l1 = data_race(atomic_long_read(&sdp->srcu_lock_count[idx]));
c0 = l0 - u0;
c1 = l1 - u1;