Re: [PATCH 16/36] rcu: Fix rcu_idle_exit()
, Arnd Bergmann , ulli.kr...@googlemail.com, vgu...@kernel.org,
linux-...@vger.kernel.org, j...@joshtriplett.org, rost...@goodmis.org,
r...@vger.kernel.org, b...@alien8.de, bc...@quicinc.com,
tsbog...@alpha.franken.de, linux-par...@vger.kernel.org, sudeep.ho...@arm.com,
shawn...@kernel.org, da...@davemloft.net, dal...@libc.org, t...@atomide.com,
amakha...@vmware.com, bjorn.anders...@linaro.org, h...@zytor.com,
sparcli...@vger.kernel.org, linux-hexa...@vger.kernel.org,
linux-ri...@lists.infradead.org, anton.iva...@cambridgegreys.com,
jo...@southpole.se, yury.no...@gmail.com, rich...@nod.at, x...@kernel.org,
li...@armlinux.org.uk, mi...@redhat.com, a...@eecs.berkeley.edu,
h...@linux.ibm.com, stefan.kristians...@saunalahti.fi,
openr...@lists.librecores.org, paul.walms...@sifive.com,
linux-te...@vger.kernel.org, namhy...@kernel.org,
andriy.shevche...@linux.intel.com, jpoim...@kernel.org, jgr...@suse.com,
mon...@monstr.eu, linux-m...@vger.kernel.org, pal...@dabbelt.com, anup@brain
fault.org, i...@jurassic.park.msu.ru, johan...@sipsolutions.net,
linuxppc-dev@lists.ozlabs.org
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On Wed, Jun 08, 2022 at 04:27:39PM +0200, Peter Zijlstra wrote:
> Current rcu_idle_exit() is terminally broken because it uses
> local_irq_{save,restore}(), which are traced which uses RCU.
>
> However, now that all the callers are sure to have IRQs disabled, we
> can remove these calls.
>
> Signed-off-by: Peter Zijlstra (Intel)
> Acked-by: Paul E. McKenney
We have some fun conflicts between this series and Frederic's context-tracking
series. But it looks like these can be resolved by:
1. A patch on top of Frederic's series that provides the old rcu_*()
names for the functions now prefixed with ct_*() such as
ct_idle_exit().
2. Another patch on top of Frederic's series that takes the
changes remaining from this patch, shown below. Frederic's
series uses raw_local_irq_save() and raw_local_irq_restore(),
which can then be removed.
Or is there a better way to do this?
Thanx, Paul
commit f64cee8c159e9863a74594efe3d33fb513a6a7b5
Author: Peter Zijlstra
Date: Tue Jun 14 17:24:43 2022 -0700
context_tracking: Interrupts always disabled for ct_idle_exit()
Now that the idle-loop cleanups have ensured that rcu_idle_exit() is
always invoked with interrupts disabled, remove the interrupt disabling
in favor of a debug check.
Signed-off-by: Peter Zijlstra
Cc: Frederic Weisbecker
Signed-off-by: Paul E. McKenney
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 1da44803fd319..99310cf5b0254 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -332,11 +332,8 @@ EXPORT_SYMBOL_GPL(ct_idle_enter);
*/
void noinstr ct_idle_exit(void)
{
- unsigned long flags;
-
- raw_local_irq_save(flags);
+ WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !raw_irqs_disabled());
ct_kernel_enter(false, RCU_DYNTICKS_IDX - CONTEXT_IDLE);
- raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(ct_idle_exit);
Re: [PATCH 16/36] rcu: Fix rcu_idle_exit()
arndb.de>, ulli.kr...@googlemail.com, vgu...@kernel.org,
linux-...@vger.kernel.org, j...@joshtriplett.org, rost...@goodmis.org,
r...@vger.kernel.org, b...@alien8.de, bc...@quicinc.com,
tsbog...@alpha.franken.de, linux-par...@vger.kernel.org, sudeep.ho...@arm.com,
shawn...@kernel.org, da...@davemloft.net, dal...@libc.org, t...@atomide.com,
amakha...@vmware.com, bjorn.anders...@linaro.org, h...@zytor.com,
sparcli...@vger.kernel.org, linux-hexa...@vger.kernel.org,
linux-ri...@lists.infradead.org, anton.iva...@cambridgegreys.com,
jo...@southpole.se, yury.no...@gmail.com, rich...@nod.at, x...@kernel.org,
li...@armlinux.org.uk, mi...@redhat.com, a...@eecs.berkeley.edu,
paul...@kernel.org, h...@linux.ibm.com, stefan.kristians...@saunalahti.fi,
openr...@lists.librecores.org, paul.walms...@sifive.com,
linux-te...@vger.kernel.org, namhy...@kernel.org,
andriy.shevche...@linux.intel.com, jpoim...@kernel.org, jgr...@suse.com,
mon...@monstr.eu, linux-m...@vger.kernel.org, pal...@dabbelt.com, anup@brainfa
ult.org, i...@jurassic.park.msu.ru, johan...@sipsolutions.net,
linuxppc-dev@lists.ozlabs.org
Errors-To: linuxppc-dev-bounces+archive=mail-archive@lists.ozlabs.org
Sender: "Linuxppc-dev"
On Wed, Jun 08, 2022 at 04:27:39PM +0200, Peter Zijlstra wrote:
> Current rcu_idle_exit() is terminally broken because it uses
> local_irq_{save,restore}(), which are traced which uses RCU.
>
> However, now that all the callers are sure to have IRQs disabled, we
> can remove these calls.
>
> Signed-off-by: Peter Zijlstra (Intel)
> Acked-by: Paul E. McKenney
Acked-by: Mark Rutland
Mark.
> ---
> kernel/rcu/tree.c |9 +++--
> 1 file changed, 3 insertions(+), 6 deletions(-)
>
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -659,7 +659,7 @@ static noinstr void rcu_eqs_enter(bool u
> * If you add or remove a call to rcu_idle_enter(), be sure to test with
> * CONFIG_RCU_EQS_DEBUG=y.
> */
> -void rcu_idle_enter(void)
> +void noinstr rcu_idle_enter(void)
> {
> lockdep_assert_irqs_disabled();
> rcu_eqs_enter(false);
> @@ -896,13 +896,10 @@ static void noinstr rcu_eqs_exit(bool us
> * If you add or remove a call to rcu_idle_exit(), be sure to test with
> * CONFIG_RCU_EQS_DEBUG=y.
> */
> -void rcu_idle_exit(void)
> +void noinstr rcu_idle_exit(void)
> {
> - unsigned long flags;
> -
> - local_irq_save(flags);
> + lockdep_assert_irqs_disabled();
> rcu_eqs_exit(false);
> - local_irq_restore(flags);
> }
> EXPORT_SYMBOL_GPL(rcu_idle_exit);
>
>
>
[PATCH 16/36] rcu: Fix rcu_idle_exit()
, Arnd Bergmann , ulli.kr...@googlemail.com, vgu...@kernel.org,
linux-...@vger.kernel.org, j...@joshtriplett.org, rost...@goodmis.org,
r...@vger.kernel.org, b...@alien8.de, bc...@quicinc.com,
tsbog...@alpha.franken.de, linux-par...@vger.kernel.org, sudeep.ho...@arm.com,
shawn...@kernel.org, da...@davemloft.net, dal...@libc.org, t...@atomide.com,
amakha...@vmware.com, bjorn.anders...@linaro.org, h...@zytor.com,
sparcli...@vger.kernel.org, linux-hexa...@vger.kernel.org,
linux-ri...@lists.infradead.org, anton.iva...@cambridgegreys.com,
jo...@southpole.se, yury.no...@gmail.com, rich...@nod.at, x...@kernel.org,
li...@armlinux.org.uk, mi...@redhat.com, a...@eecs.berkeley.edu,
paul...@kernel.org, h...@linux.ibm.com, stefan.kristians...@saunalahti.fi,
openr...@lists.librecores.org, paul.walms...@sifive.com,
linux-te...@vger.kernel.org, namhy...@kernel.org,
andriy.shevche...@linux.intel.com, jpoim...@kernel.org, jgr...@suse.com,
mon...@monstr.eu, linux-m...@vger.kernel.org, palmer@dab
belt.com, a...@brainfault.org, i...@jurassic.park.msu.ru,
johan...@sipsolutions.net, linuxppc-dev@lists.ozlabs.org
Errors-To: linuxppc-dev-bounces+archive=mail-archive@lists.ozlabs.org
Sender: "Linuxppc-dev"
Current rcu_idle_exit() is terminally broken because it uses
local_irq_{save,restore}(), which are traced which uses RCU.
However, now that all the callers are sure to have IRQs disabled, we
can remove these calls.
Signed-off-by: Peter Zijlstra (Intel)
Acked-by: Paul E. McKenney
---
kernel/rcu/tree.c |9 +++--
1 file changed, 3 insertions(+), 6 deletions(-)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -659,7 +659,7 @@ static noinstr void rcu_eqs_enter(bool u
* If you add or remove a call to rcu_idle_enter(), be sure to test with
* CONFIG_RCU_EQS_DEBUG=y.
*/
-void rcu_idle_enter(void)
+void noinstr rcu_idle_enter(void)
{
lockdep_assert_irqs_disabled();
rcu_eqs_enter(false);
@@ -896,13 +896,10 @@ static void noinstr rcu_eqs_exit(bool us
* If you add or remove a call to rcu_idle_exit(), be sure to test with
* CONFIG_RCU_EQS_DEBUG=y.
*/
-void rcu_idle_exit(void)
+void noinstr rcu_idle_exit(void)
{
- unsigned long flags;
-
- local_irq_save(flags);
+ lockdep_assert_irqs_disabled();
rcu_eqs_exit(false);
- local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(rcu_idle_exit);
