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| author |   Paul E. McKenney <paulmck@kernel.org> | 2020-03-20 14:29:08 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-04-27 11:03:52 -0700 |
| commit | b38f57c1fe64276773b124dffb0a139cc32ab3cb (patch) | |
| tree | b69915f8632122f65bc6a692bf8edfbec71228ff /kernel/rcu | |
| parent | rcu-tasks: Avoid IPIing userspace/idle tasks if kernel is so built (diff) | |
| download | linux-dev-b38f57c1fe64276773b124dffb0a139cc32ab3cb.tar.xz linux-dev-b38f57c1fe64276773b124dffb0a139cc32ab3cb.zip | |
rcu-tasks: Allow rcu_read_unlock_trace() under scheduler locks
The rcu_read_unlock_trace() can invoke rcu_read_unlock_trace_special(),
which in turn can call wake_up(). Therefore, if any scheduler lock is
held across a call to rcu_read_unlock_trace(), self-deadlock can occur.
This commit therefore uses the irq_work facility to defer the wake_up()
to a clean environment where no scheduler locks will be held.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
[ paulmck: Update #includes for m68k per kbuild test robot. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tasks.h | 12 | ||||
| -rw-r--r-- | kernel/rcu/update.c | 1 |
2 files changed, 12 insertions, 1 deletions
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index a9e8ecb10860..dd311e93ed0f 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -729,6 +729,16 @@ void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func); DEFINE_RCU_TASKS(rcu_tasks_trace, rcu_tasks_wait_gp, call_rcu_tasks_trace, "RCU Tasks Trace"); +/* + * This irq_work handler allows rcu_read_unlock_trace() to be invoked + * while the scheduler locks are held. + */ +static void rcu_read_unlock_iw(struct irq_work *iwp) +{ + wake_up(&trc_wait); +} +static DEFINE_IRQ_WORK(rcu_tasks_trace_iw, rcu_read_unlock_iw); + /* If we are the last reader, wake up the grace-period kthread. */ void rcu_read_unlock_trace_special(struct task_struct *t, int nesting) { @@ -742,7 +752,7 @@ void rcu_read_unlock_trace_special(struct task_struct *t, int nesting) WRITE_ONCE(t->trc_reader_special.b.need_qs, false); WRITE_ONCE(t->trc_reader_nesting, nesting); if (nq && atomic_dec_and_test(&trc_n_readers_need_end)) - wake_up(&trc_wait); + irq_work_queue(&rcu_tasks_trace_iw); } EXPORT_SYMBOL_GPL(rcu_read_unlock_trace_special); diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index c5799349ff31..b1f07a0e3a56 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -41,6 +41,7 @@ #include <linux/sched/isolation.h> #include <linux/kprobes.h> #include <linux/slab.h> +#include <linux/irq_work.h> #define CREATE_TRACE_POINTS |