From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Karl Mehltretter <kmehltretter@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@kernel.org>, Harry Yoo <harry@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Boqun Feng <boqun@kernel.org>, Waiman Long <longman@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
David Hildenbrand <david@kernel.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Shakeel Butt <shakeel.butt@linux.dev>,
David Stevens <stevensd@google.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Shuah Khan <shuah@kernel.org>, Amery Hung <ameryhung@gmail.com>,
Swaraj Gaikwad <swarajgaikwad1925@gmail.com>,
Clark Williams <clrkwllms@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-mm@kvack.org, linux-rt-devel@lists.linux.dev,
bpf@vger.kernel.org, linux-kselftest@vger.kernel.org,
cgroups@vger.kernel.org
Subject: Re: [RFC PATCH v2 0/3] locking, mm: Add atomic allocator trylocks on RT
Date: Tue, 20 Oct 2026 17:27:08 +0200 [thread overview]
Message-ID: <20261020152708.3atPlnSl@linutronix.de> (raw)
In-Reply-To: <20261005070625.8871-1-kmehltretter@gmail.com>
On 2026-10-05 09:06:22 [+0200], Karl Mehltretter wrote:
> On PREEMPT_RT, a BPF task-storage program attached to sched_waking
> can deadlock when kmalloc_nolock() obtains an rtmutex-backed allocator
> spinlock while try_to_wake_up() holds p->pi_lock. Releasing the allocator
> lock can enter priority-inheritance or wakeup code and re-enter scheduler
> locking.
What is it that you try to achieve and why. Why is !PREEMPT_RT not
affected? Half of the problems origin from PI-boosst.
Why has the nolock an rmutex-backed allocator.
can_spin_trylock() skips hardirq and NMI. There is a trylock on the
local_lock_t.
Why do we have this mess and couldn't we avoid having it?
I looked at the patches and there something about hardirq-atomic waiter.
Wen don't have this. I don't think we want.
Sebastian
prev parent reply other threads:[~2026-10-20 15:27 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-05 7:06 Karl Mehltretter
2026-10-05 7:06 ` [RFC PATCH v2 1/3] locking/rtmutex: Support atomic PREEMPT_RT spin trylocks Karl Mehltretter
2026-10-05 7:06 ` [RFC PATCH v2 2/3] mm: use atomic RT trylocks for no-lock allocation Karl Mehltretter
2026-10-05 7:06 ` [RFC PATCH v2 3/3] selftests/bpf: exercise task storage from hrtimer_start Karl Mehltretter
2026-10-05 7:53 ` bot+bpf-ci
2026-10-07 17:15 ` [RFC PATCH v2 0/3] locking, mm: Add atomic allocator trylocks on RT Harry Yoo
2026-10-09 10:04 ` Karl Mehltretter
2026-10-20 2:14 ` Karl Mehltretter
2026-10-20 15:27 ` Sebastian Andrzej Siewior [this message]
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