Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions | Date | Tue, 3 May 2022 12:00:33 +0200 |
| |
Some RCU functions enter or exit into/from RCU idle mode while using trace-able and lockdep-aware IRQs (un-)masking. This could be easily solved with using raw versions of local_irq_*() but we would then lose some precious debugging informations.
Another possible way to solve this may consist in using rude RCU-tasks in lockdep and irqsoff tracing.
In any case and until this get solved, those RCU functions can't get tagged as noinstr even though they should.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com> Cc: Uladzislau Rezki <uladzislau.rezki@sony.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Nicolas Saenz Julienne <nsaenz@kernel.org> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com> Cc: Yu Liao<liaoyu15@huawei.com> Cc: Phil Auld <pauld@redhat.com> Cc: Paul Gortmaker<paul.gortmaker@windriver.com> Cc: Alex Belits <abelits@marvell.com> --- kernel/rcu/tree.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index a5da4b87afde..2a6e7723fc4d 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -838,6 +838,10 @@ void rcu_irq_exit_check_preempt(void) * * If you add or remove a call to rcu_irq_exit_irqson(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. + * + * FIXME: This function should be noinstr but the below local_irq_restore() is + * unsafe because it involves illegal RCU uses through tracing and lockdep. + * This must be fixed first. */ void rcu_irq_exit_irqson(void) { @@ -895,6 +899,10 @@ static void noinstr rcu_eqs_exit(bool user) * * If you add or remove a call to rcu_idle_exit(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. + * + * FIXME: This function should be noinstr but the below local_irq_save() is + * unsafe because it involves illegal RCU uses through tracing and lockdep. + * This must be fixed first. */ void rcu_idle_exit(void) { @@ -1076,6 +1084,10 @@ noinstr void rcu_irq_enter(void) * * If you add or remove a call to rcu_irq_enter_irqson(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. + * + * FIXME: This function should be noinstr but the below local_irq_save() is + * unsafe because it involves illegal RCU uses through tracing and lockdep. + * This must be fixed first. */ void rcu_irq_enter_irqson(void) { -- 2.25.1
| |