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    Subject[PATCH tip/core/rcu 32/88] rcu: Add preemptibility checks in rcu_sched_qs() and rcu_bh_qs()
    Date
    This commit adds WARN_ON_ONCE() calls that trigger if either
    rcu_sched_qs() or rcu_bh_qs() are invoked with preemption enabled.
    In the immortal words of Peter Zijlstra: "these are much harder to ignore
    than comments".

    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    ---
    kernel/rcu/tree.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
    index 3bee58fc23b1..b01a02e7a0b7 100644
    --- a/kernel/rcu/tree.c
    +++ b/kernel/rcu/tree.c
    @@ -250,6 +250,7 @@ static int rcu_gp_in_progress(struct rcu_state *rsp)
    */
    void rcu_sched_qs(void)
    {
    + RCU_LOCKDEP_WARN(preemptible(), "rcu_sched_qs() invoked with preemption enabled!!!");
    if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.s))
    return;
    trace_rcu_grace_period(TPS("rcu_sched"),
    @@ -265,6 +266,7 @@ void rcu_sched_qs(void)

    void rcu_bh_qs(void)
    {
    + RCU_LOCKDEP_WARN(preemptible(), "rcu_bh_qs() invoked with preemption enabled!!!");
    if (__this_cpu_read(rcu_bh_data.cpu_no_qs.s)) {
    trace_rcu_grace_period(TPS("rcu_bh"),
    __this_cpu_read(rcu_bh_data.gpnum),
    --
    2.5.2
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