From: Sebastian Sewior <bigeasy@linutronix.de>
To: Michal Hocko <mhocko@suse.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Matthew Wilcox <willy@infradead.org>, bpf <bpf@vger.kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Vlastimil Babka <vbabka@suse.cz>,
Steven Rostedt <rostedt@goodmis.org>,
Hou Tao <houtao1@huawei.com>,
Johannes Weiner <hannes@cmpxchg.org>,
shakeel.butt@linux.dev, Thomas Gleixner <tglx@linutronix.de>,
Tejun Heo <tj@kernel.org>, linux-mm <linux-mm@kvack.org>,
Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH bpf-next v2 1/6] mm, bpf: Introduce __GFP_TRYLOCK for opportunistic page allocation
Date: Thu, 12 Dec 2024 16:35:06 +0100 [thread overview]
Message-ID: <20241212153506.dT1MvukO@linutronix.de> (raw)
In-Reply-To: <Z1r_eKGkJYMz-uwH@tiehlicka>
On 2024-12-12 16:21:28 [+0100], Michal Hocko wrote:
> On Thu 12-12-24 16:07:44, Sebastian Sewior wrote:
> > But since I see in_nmi(). You can't trylock from NMI on RT. The trylock
> > part is easy but unlock might need to acquire rt_mutex_base::wait_lock
> > and worst case is to wake a waiter via wake_up_process().
>
> Ohh, I didn't realize that. So try_lock would only be safe on
> raw_spin_lock right?
If NMI is one of the possible calling contexts, yes.
One thing I am not 100% sure about is how "good" a spinlock_t trylock is
if attempted from hardirq (on PREEMPT_RT). Obtaining the lock und
unlocking is doable. The lock part will assign the "current" task as the
task that owns the lock now. This task is just randomly on the CPU while
the hardirq triggered. The regular spin_lock() will see this random task
as the owner and might PI-boost it. This could work…
Sebastian
next prev parent reply other threads:[~2024-12-12 15:35 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-10 2:39 [PATCH bpf-next v2 0/6] bpf, mm: Introduce __GFP_TRYLOCK Alexei Starovoitov
2024-12-10 2:39 ` [PATCH bpf-next v2 1/6] mm, bpf: Introduce __GFP_TRYLOCK for opportunistic page allocation Alexei Starovoitov
2024-12-10 5:31 ` Matthew Wilcox
2024-12-10 9:05 ` Michal Hocko
2024-12-10 20:25 ` Shakeel Butt
2024-12-11 10:08 ` Michal Hocko
2024-12-10 22:06 ` Alexei Starovoitov
2024-12-11 10:19 ` Michal Hocko
2024-12-12 15:07 ` Sebastian Sewior
2024-12-12 15:21 ` Michal Hocko
2024-12-12 15:35 ` Sebastian Sewior [this message]
2024-12-12 15:48 ` Steven Rostedt
2024-12-12 16:00 ` Sebastian Sewior
2024-12-13 17:44 ` Steven Rostedt
2024-12-13 18:44 ` Alexei Starovoitov
2024-12-13 18:57 ` Alexei Starovoitov
2024-12-13 20:09 ` Steven Rostedt
2024-12-13 21:00 ` Steven Rostedt
2024-12-13 22:02 ` Alexei Starovoitov
2024-12-12 21:57 ` Alexei Starovoitov
2024-12-10 21:42 ` Alexei Starovoitov
2024-12-10 9:01 ` Sebastian Andrzej Siewior
2024-12-10 21:53 ` Alexei Starovoitov
2024-12-11 8:38 ` Vlastimil Babka
2024-12-12 2:14 ` Alexei Starovoitov
2024-12-12 8:54 ` Vlastimil Babka
2024-12-10 18:39 ` Vlastimil Babka
2024-12-10 22:42 ` Alexei Starovoitov
2024-12-11 8:48 ` Vlastimil Babka
2024-12-10 2:39 ` [PATCH bpf-next v2 2/6] mm, bpf: Introduce free_pages_nolock() Alexei Starovoitov
2024-12-10 8:35 ` Sebastian Andrzej Siewior
2024-12-10 22:49 ` Alexei Starovoitov
2024-12-12 14:44 ` Sebastian Andrzej Siewior
2024-12-12 19:57 ` Alexei Starovoitov
2024-12-11 10:11 ` Vlastimil Babka
2024-12-12 1:43 ` Alexei Starovoitov
2024-12-10 2:39 ` [PATCH bpf-next v2 3/6] locking/local_lock: Introduce local_trylock_irqsave() Alexei Starovoitov
2024-12-11 10:53 ` Vlastimil Babka
2024-12-11 11:55 ` Vlastimil Babka
2024-12-12 2:49 ` Alexei Starovoitov
2024-12-12 9:15 ` Vlastimil Babka
2024-12-13 14:02 ` Vlastimil Babka
2024-12-12 15:15 ` Sebastian Andrzej Siewior
2024-12-12 19:59 ` Alexei Starovoitov
2024-12-10 2:39 ` [PATCH bpf-next v2 4/6] memcg: Add __GFP_TRYLOCK support Alexei Starovoitov
2024-12-11 23:47 ` kernel test robot
2024-12-10 2:39 ` [PATCH bpf-next v2 5/6] mm, bpf: Use __GFP_ACCOUNT in try_alloc_pages() Alexei Starovoitov
2024-12-11 12:05 ` Vlastimil Babka
2024-12-12 2:54 ` Alexei Starovoitov
2024-12-10 2:39 ` [PATCH bpf-next v2 6/6] bpf: Use try_alloc_pages() to allocate pages for bpf needs Alexei Starovoitov
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