linux-kernel - [REGRESSION] bisected: perf: hang when using async-profiler caused by perf: Fix the POLL

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Message-ID: <CAHPNGSQpXEopYreir+uDDEbtXTBvBvi8c6fYXJvceqtgTPao3Q@mail.gmail.com>
Date: Sat, 11 Oct 2025 01:31:37 -0700
From: Octavia Togami <octavia.togami@...il.com>
To: stable@...r.kernel.org
Cc: regressions@...ts.linux.dev, peterz@...radead.org, 
	linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: [REGRESSION] bisected: perf: hang when using async-profiler caused by
 perf: Fix the POLL_HUP delivery breakage

Using async-profiler
(https://github.com/async-profiler/async-profiler/) on Linux
6.17.1-arch1-1 causes a complete hang of the CPU. This has been
reported by many people at https://github.com/lucko/spark/issues/530.
spark is a piece of software that uses async-profiler internally.

As seen in https://github.com/lucko/spark/issues/530#issuecomment-3339974827,
this was bisected to 18dbcbfabfffc4a5d3ea10290c5ad27f22b0d240 perf:
Fix the POLL_HUP delivery breakage. Reverting this commit on 6.17.1
fixed the issue for me.

Steps to reproduce:
1. Get a copy of async-profiler. I tested both v3 (affects older spark
versions) and v4.1 (latest at time of writing). Unarchive it, this is
<async-profiler-dir>.
2. Set kernel parameters kernel.perf_event_paranoid=1 and
kernel.kptr_restrict=0 as instructed by
https://github.com/async-profiler/async-profiler/blob/fb673227c7fb311f872ce9566769b006b357ecbe/docs/GettingStarted.md
3. Install a version of Java that comes with jshell, i.e. Java 9 or
newer. Note: jshell is used for ease of reproduction. Any Java
application that is actively running will work.
4. Run `printf 'int acc; while (true) { acc++; }' | jshell -`. This
will start an infinitely running Java process.
5. Run `jps` and take the PID next to the text RemoteExecutionControl
-- this is the process that was just started.
6. Attach async-profiler to this process by running
`<async-profiler-dir>/bin/asprof -d 1 <PID>`. This will run for one
second, then the system should freeze entirely shortly thereafter.

I triggered a sysrq crash while the system was frozen, and the output
I found in journalctl afterwards is at
https://gist.github.com/octylFractal/76611ee76060051e5efc0c898dd0949e
I'm not sure if that text is actually from the triggered crash, but it
seems relevant. If needed, please tell me how to get the actual crash
report, I'm not sure where it is.

I'm using an AMD Ryzen 9 5900X 12-Core Processor. Given that I've seen
no Intel reports, it may be AMD specific. I don't have an Intel CPU on
hand to test with.

/proc/version: Linux version 6.17.1-arch1-1 (linux@...hlinux) (gcc
(GCC) 15.2.1 20250813, GNU ld (GNU Binutils) 2.45.0) #1 SMP
PREEMPT_DYNAMIC Mon, 06 Oct 2025 18:48:29 +0000
Operating System: Arch Linux
uname -mi: x86_64 unknown