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    Subject[PATCH tip/core/rcu 03/47] rcu: Add lockdep-RCU checks for simple self-deadlock
    Date
    From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

    It is illegal to have a grace period within a same-flavor RCU read-side
    critical section, so this commit adds lockdep-RCU checks to splat when
    such abuse is encountered. This commit does not detect more elaborate
    RCU deadlock situations. These situations might be a job for lockdep
    enhancements.

    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    ---
    kernel/rcutiny.c | 4 ++++
    kernel/rcutiny_plugin.h | 5 +++++
    kernel/rcutree.c | 8 ++++++++
    kernel/rcutree_plugin.h | 4 ++++
    kernel/srcu.c | 6 ++++++
    5 files changed, 27 insertions(+), 0 deletions(-)

    diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
    index 977296d..8e00d46 100644
    --- a/kernel/rcutiny.c
    +++ b/kernel/rcutiny.c
    @@ -319,6 +319,10 @@ static void rcu_process_callbacks(struct softirq_action *unused)
    */
    void synchronize_sched(void)
    {
    + rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
    + !lock_is_held(&rcu_lock_map) &&
    + !lock_is_held(&rcu_sched_lock_map),
    + "Illegal synchronize_sched() in RCU read-side critical section");
    cond_resched();
    }
    EXPORT_SYMBOL_GPL(synchronize_sched);
    diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
    index 9cb1ae4..4b90540 100644
    --- a/kernel/rcutiny_plugin.h
    +++ b/kernel/rcutiny_plugin.h
    @@ -706,6 +706,11 @@ EXPORT_SYMBOL_GPL(call_rcu);
    */
    void synchronize_rcu(void)
    {
    + rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
    + !lock_is_held(&rcu_lock_map) &&
    + !lock_is_held(&rcu_sched_lock_map),
    + "Illegal synchronize_rcu() in RCU read-side critical section");
    +
    #ifdef CONFIG_DEBUG_LOCK_ALLOC
    if (!rcu_scheduler_active)
    return;
    diff --git a/kernel/rcutree.c b/kernel/rcutree.c
    index 6c4a672..3cf713a 100644
    --- a/kernel/rcutree.c
    +++ b/kernel/rcutree.c
    @@ -1816,6 +1816,10 @@ EXPORT_SYMBOL_GPL(call_rcu_bh);
    */
    void synchronize_sched(void)
    {
    + rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
    + !lock_is_held(&rcu_lock_map) &&
    + !lock_is_held(&rcu_sched_lock_map),
    + "Illegal synchronize_sched() in RCU-sched read-side critical section");
    if (rcu_blocking_is_gp())
    return;
    wait_rcu_gp(call_rcu_sched);
    @@ -1833,6 +1837,10 @@ EXPORT_SYMBOL_GPL(synchronize_sched);
    */
    void synchronize_rcu_bh(void)
    {
    + rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
    + !lock_is_held(&rcu_lock_map) &&
    + !lock_is_held(&rcu_sched_lock_map),
    + "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section");
    if (rcu_blocking_is_gp())
    return;
    wait_rcu_gp(call_rcu_bh);
    diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
    index 8bb35d7..3680b6b 100644
    --- a/kernel/rcutree_plugin.h
    +++ b/kernel/rcutree_plugin.h
    @@ -688,6 +688,10 @@ EXPORT_SYMBOL_GPL(call_rcu);
    */
    void synchronize_rcu(void)
    {
    + rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
    + !lock_is_held(&rcu_lock_map) &&
    + !lock_is_held(&rcu_sched_lock_map),
    + "Illegal synchronize_rcu() in RCU read-side critical section");
    if (!rcu_scheduler_active)
    return;
    wait_rcu_gp(call_rcu);
    diff --git a/kernel/srcu.c b/kernel/srcu.c
    index 0febf61..3f99fa0 100644
    --- a/kernel/srcu.c
    +++ b/kernel/srcu.c
    @@ -172,6 +172,12 @@ static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
    {
    int idx;

    + rcu_lockdep_assert(!lock_is_held(&sp->dep_map) &&
    + !lock_is_held(&rcu_bh_lock_map) &&
    + !lock_is_held(&rcu_lock_map) &&
    + !lock_is_held(&rcu_sched_lock_map),
    + "Illegal synchronize_srcu() in same-type SRCU (or RCU) read-side critical section");
    +
    idx = sp->completed;
    mutex_lock(&sp->mutex);

    --
    1.7.8


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