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rcu: allow nesting of rcu_read_lock/rcu_read_unlock 

Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2015-01-13 17:34:15 +01:00
parent 8fda74a52b
commit d62cb4f2fd
2 changed files with 16 additions and 1 deletions
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15
include/qemu/rcu.h
View File

@ -68,6 +68,9 @@ struct rcu_reader_data {
unsigned long ctr;
bool waiting;
/* Data used by reader only */
unsigned depth;
/* Data used for registry, protected by rcu_gp_lock */
QLIST_ENTRY(rcu_reader_data) node;
};
@ -77,8 +80,13 @@ extern __thread struct rcu_reader_data rcu_reader;
static inline void rcu_read_lock(void)
{
struct rcu_reader_data *p_rcu_reader = &rcu_reader;
unsigned ctr;
unsigned ctr = atomic_read(&rcu_gp_ctr);
if (p_rcu_reader->depth++ > 0) {
return;
}
ctr = atomic_read(&rcu_gp_ctr);
atomic_xchg(&p_rcu_reader->ctr, ctr);
if (atomic_read(&p_rcu_reader->waiting)) {
atomic_set(&p_rcu_reader->waiting, false);
@ -90,6 +98,11 @@ static inline void rcu_read_unlock(void)
{
struct rcu_reader_data *p_rcu_reader = &rcu_reader;
assert(p_rcu_reader->depth != 0);
if (--p_rcu_reader->depth > 0) {
return;
}
atomic_xchg(&p_rcu_reader->ctr, 0);
if (atomic_read(&p_rcu_reader->waiting)) {
atomic_set(&p_rcu_reader->waiting, false);

2
tests/rcutorture.c
View File

@ -255,9 +255,11 @@ static void *rcu_read_stress_test(void *arg)
if (p->mbtest == 0) {
n_mberror++;
}
rcu_read_lock();
for (i = 0; i < 100; i++) {
garbage++;
}
rcu_read_unlock();
pc = p->pipe_count;
rcu_read_unlock();
if ((pc > RCU_STRESS_PIPE_LEN) || (pc < 0)) {