Commit d62cb4f2 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

rcu: allow nesting of rcu_read_lock/rcu_read_unlock 



Reviewed-by: default avatarFam Zheng <famz@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 8fda74a5

include/qemu/rcu.h

+14 −1
Original line number Diff line number Diff line
@@ -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;



    if (p_rcu_reader->depth++ > 0) {

        return;

    }



    unsigned ctr = atomic_read(&rcu_gp_ctr);

    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);

tests/rcutorture.c

+2 −0
Original line number Diff line number Diff line
@@ -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)) {