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| author | Frederic Weisbecker <frederic@kernel.org> | 2021-02-01 02:05:45 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-03-04 13:38:35 +0300 |
| commit | e713bdd791ba9d11980fc52e080ed68c4b7527a5 (patch) | |
| tree | 45967043144b64be4e8bbb9a3690a0b887102d87 /kernel/rcu | |
| parent | 20b7669fa3f0511c2985f9483d87a65bcb13eb47 (diff) | |
| download | linux-e713bdd791ba9d11980fc52e080ed68c4b7527a5.tar.xz | |
rcu/nocb: Perform deferred wake up before last idle's need_resched() check
commit 43789ef3f7d61aa7bed0cb2764e588fc990c30ef upstream.
Entering RCU idle mode may cause a deferred wake up of an RCU NOCB_GP
kthread (rcuog) to be serviced.
Usually a local wake up happening while running the idle task is handled
in one of the need_resched() checks carefully placed within the idle
loop that can break to the scheduler.
Unfortunately the call to rcu_idle_enter() is already beyond the last
generic need_resched() check and we may halt the CPU with a resched
request unhandled, leaving the task hanging.
Fix this with splitting the rcuog wakeup handling from rcu_idle_enter()
and place it before the last generic need_resched() check in the idle
loop. It is then assumed that no call to call_rcu() will be performed
after that in the idle loop until the CPU is put in low power mode.
Fixes: 96d3fd0d315a (rcu: Break call_rcu() deadlock involving scheduler and perf)
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210131230548.32970-3-frederic@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 3 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 5 |
2 files changed, 5 insertions, 3 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index db6b2970f5e3..5dc36c6e80fd 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -663,10 +663,7 @@ static noinstr void rcu_eqs_enter(bool user) */ void rcu_idle_enter(void) { - struct rcu_data *rdp = this_cpu_ptr(&rcu_data); - lockdep_assert_irqs_disabled(); - do_nocb_deferred_wakeup(rdp); rcu_eqs_enter(false); } EXPORT_SYMBOL_GPL(rcu_idle_enter); diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index fd8a52e9a887..7d4f78bf4057 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2187,6 +2187,11 @@ static void do_nocb_deferred_wakeup(struct rcu_data *rdp) do_nocb_deferred_wakeup_common(rdp); } +void rcu_nocb_flush_deferred_wakeup(void) +{ + do_nocb_deferred_wakeup(this_cpu_ptr(&rcu_data)); +} + void __init rcu_init_nohz(void) { int cpu; |