Subject: [PATCH] perf/core: Add SRCU annotation for pmus list walk

Since commit
28875945ba98d ("rcu: Add support for consolidated-RCU reader checking")

there is an additional check to ensure that a RCU related lock is held
while the RCU list is iterated.
This section holds the SRCU reader lock instead.

Add annotation to list_for_each_entry_rcu() that pmus_srcu must be
acquired during the list traversal.

Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
---

I see the warning in in v5.4-rc during boot. For some reason I don't see
it in tip/master during boot but "perf stat w" triggers it again (among
other things).

kernel/events/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5224388872069..dbb3b26a55612 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10497,7 +10497,7 @@ static struct pmu *perf_init_event(struct perf_event *event)
goto unlock;
}

- list_for_each_entry_rcu(pmu, &pmus, entry) {
+ list_for_each_entry_rcu(pmu, &pmus, entry, lockdep_is_held(&pmus_srcu)) {
ret = perf_try_init_event(pmu, event);
if (!ret)
goto unlock;
--
2.24.0



Subject: Re: [PATCH] perf/core: Add SRCU annotation for pmus list walk

On 2019-11-19 13:14:29 [+0100], To [email protected] wrote:
> Since commit
> 28875945ba98d ("rcu: Add support for consolidated-RCU reader checking")
>
> there is an additional check to ensure that a RCU related lock is held
> while the RCU list is iterated.
> This section holds the SRCU reader lock instead.
>
> Add annotation to list_for_each_entry_rcu() that pmus_srcu must be
> acquired during the list traversal.
>
> Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
> ---
>
> I see the warning in in v5.4-rc during boot. For some reason I don't see
> it in tip/master during boot but "perf stat w" triggers it again (among
> other things).

ping.

> kernel/events/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 5224388872069..dbb3b26a55612 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -10497,7 +10497,7 @@ static struct pmu *perf_init_event(struct perf_event *event)
> goto unlock;
> }
>
> - list_for_each_entry_rcu(pmu, &pmus, entry) {
> + list_for_each_entry_rcu(pmu, &pmus, entry, lockdep_is_held(&pmus_srcu)) {
> ret = perf_try_init_event(pmu, event);
> if (!ret)
> goto unlock;

Sebastian

2019-11-29 20:06:47

by Joel Fernandes

[permalink] [raw]
Subject: Re: [PATCH] perf/core: Add SRCU annotation for pmus list walk

On Tue, Nov 19, 2019 at 01:14:29PM +0100, Sebastian Andrzej Siewior wrote:
> Since commit
> 28875945ba98d ("rcu: Add support for consolidated-RCU reader checking")
>
> there is an additional check to ensure that a RCU related lock is held
> while the RCU list is iterated.
> This section holds the SRCU reader lock instead.
>
> Add annotation to list_for_each_entry_rcu() that pmus_srcu must be
> acquired during the list traversal.
>

Reviewed-by: Joel Fernandes (Google) <[email protected]>

thanks,

- Joel

> Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
> ---
>
> I see the warning in in v5.4-rc during boot. For some reason I don't see
> it in tip/master during boot but "perf stat w" triggers it again (among
> other things).
>
> kernel/events/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 5224388872069..dbb3b26a55612 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -10497,7 +10497,7 @@ static struct pmu *perf_init_event(struct perf_event *event)
> goto unlock;
> }
>
> - list_for_each_entry_rcu(pmu, &pmus, entry) {
> + list_for_each_entry_rcu(pmu, &pmus, entry, lockdep_is_held(&pmus_srcu)) {
> ret = perf_try_init_event(pmu, event);
> if (!ret)
> goto unlock;
> --
> 2.24.0
>