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rcu-tasks: Make trc_read_check_handler() fetch ->trc_reader_nesting only once 

This commit replaces the pair of READ_ONCE(t->trc_reader_nesting) calls
with a single such call and a local variable.  This makes the code's
intent more clear.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: KP Singh <kpsingh@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-05-26 16:12:51 -07:00
parent 550611269b
commit 9ff86b4c44
1 changed files with 4 additions and 2 deletions
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6
kernel/rcu/tasks.h
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@ -1278,6 +1278,7 @@ static void trc_del_holdout(struct task_struct *t)
/* IPI handler to check task state. */
static void trc_read_check_handler(void *t_in)
{
int nesting;
struct task_struct *t = current;
struct task_struct *texp = t_in;
@ -1287,12 +1288,13 @@ static void trc_read_check_handler(void *t_in)
// If the task is not in a read-side critical section, and
// if this is the last reader, awaken the grace-period kthread.
if (likely(!READ_ONCE(t->trc_reader_nesting))) {
nesting = READ_ONCE(t->trc_reader_nesting);
if (likely(!nesting)) {
rcu_trc_cmpxchg_need_qs(t, 0, TRC_NEED_QS_CHECKED);
goto reset_ipi;
}
// If we are racing with an rcu_read_unlock_trace(), try again later.
if (unlikely(READ_ONCE(t->trc_reader_nesting) < 0))
if (unlikely(nesting < 0))
goto reset_ipi;
// Get here if the task is in a read-side critical section. Set