Hey All,
  So in testing with the full Proxy Execution series,
Vineeth Pillai managed to trip some interesting bugs which
initially looked to be KVM or RCU related[1], which he later
diagnosed as Proxy Execution related and created a useful test
driver to reproduce.

I found these same issues could be triggered with the upstream
portions of Proxy Execution, so I wanted to send along these
fixes for 7.1-rc

Again, a huge thanks to Vineeth for uncovering these issues
that have evaded all my stress testing so far!

Thanks
-john

[1]: https://lore.kernel.org/lkml/20260320125633.2290675-1-vineeth@bitbyteword.org/

Cc: Vineeth Pillai <vineethrp@google.com>
Cc: Sonam Sanju <sonam.sanju@intel.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Kunwu Chan <kunwu.chan@linux.dev>
Cc: Tejun Heo <tj@kernel.org>
Cc: Joel Fernandes <joelagnelf@nvidia.com>
Cc: Qais Yousef <qyousef@layalina.io>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Metin Kaya <Metin.Kaya@arm.com>
Cc: Xuewen Yan <xuewen.yan94@gmail.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: kuyo chang <kuyo.chang@mediatek.com>
Cc: hupu <hupu.gm@gmail.com>
Cc: kernel-team@android.com

John Stultz (2):
  sched: proxy-exec: Close race causing workqueue work being delayed
  locking: mutex: Fix proxy-exec potentially deactivating tasks marked
    TASK_RUNNING

 kernel/locking/mutex.c |  1 +
 kernel/sched/core.c    | 11 +++++++++++
 2 files changed, 12 insertions(+)

-- 
2.54.0.545.g6539524ca2-goog

April 28, 2026 at 2:38 AM, "John Stultz" <jstultz@google.com mailto:jstultz@google.com?to=%22John%20Stultz%22%20%3Cjstultz%40google.com%3E > wrote:


> 
> Hey All,
>  So in testing with the full Proxy Execution series,
> Vineeth Pillai managed to trip some interesting bugs which
> initially looked to be KVM or RCU related[1], which he later
> diagnosed as Proxy Execution related and created a useful test
> driver to reproduce.
> 
> I found these same issues could be triggered with the upstream
> portions of Proxy Execution, so I wanted to send along these
> fixes for 7.1-rc
> 
> Again, a huge thanks to Vineeth for uncovering these issues
> that have evaded all my stress testing so far!
> 
> Thanks
> -john
> 
> [1]: https://lore.kernel.org/lkml/20260320125633.2290675-1-vineeth@bitbyteword.org/
> 
Thanks John, Vineeth.

From the SRCU side, this helps explain the earlier KVM/RCU-looking
stall pattern as a downstream symptom, with trigger likely in
proxy-exec scheduler/mutex interaction.

It would be good to confirm whether the original workload still
reproduces (process_srcu pending + irqfd-side stalls) after applying
this series, and whether there is a proxy-exec on/off comparison
under the same setup.

Thanks for driving this down.

> Cc: Vineeth Pillai <vineethrp@google.com>
> Cc: Sonam Sanju <sonam.sanju@intel.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: Kunwu Chan <kunwu.chan@linux.dev>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Joel Fernandes <joelagnelf@nvidia.com>
> Cc: Qais Yousef <qyousef@layalina.io>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Vincent Guittot <vincent.guittot@linaro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Cc: Valentin Schneider <vschneid@redhat.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Will Deacon <will@kernel.org>
> Cc: Waiman Long <longman@redhat.com>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Cc: "Paul E. McKenney" <paulmck@kernel.org>
> Cc: Metin Kaya <Metin.Kaya@arm.com>
> Cc: Xuewen Yan <xuewen.yan94@gmail.com>
> Cc: K Prateek Nayak <kprateek.nayak@amd.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Cc: Suleiman Souhlal <suleiman@google.com>
> Cc: kuyo chang <kuyo.chang@mediatek.com>
> Cc: hupu <hupu.gm@gmail.com>
> Cc: kernel-team@android.com
> 
> John Stultz (2):
>  sched: proxy-exec: Close race causing workqueue work being delayed
>  locking: mutex: Fix proxy-exec potentially deactivating tasks marked
>  TASK_RUNNING
> 
>  kernel/locking/mutex.c | 1 +
>  kernel/sched/core.c | 11 +++++++++++
>  2 files changed, 12 insertions(+)
> 
> -- 
> 2.54.0.545.g6539524ca2-goog
>