linux-kernel - Re: [PATCH 1/2] hung_task: Show the blocker task if the task is hung on mutex

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Message-ID: <20250220113018.5d5b4fb9@gandalf.local.home>
Date: Thu, 20 Feb 2025 11:30:18 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Waiman Long <llong@...hat.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>, Peter Zijlstra
 <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Will Deacon
 <will@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, Boqun Feng
 <boqun.feng@...il.com>, Joel Granados <joel.granados@...nel.org>, Anna
 Schumaker <anna.schumaker@...cle.com>, Lance Yang <ioworker0@...il.com>,
 Kent Overstreet <kent.overstreet@...ux.dev>, Yongliang Gao
 <leonylgao@...cent.com>, Tomasz Figa <tfiga@...omium.org>, Sergey
 Senozhatsky <senozhatsky@...omium.org>, linux-kernel@...r.kernel.org, Linux
 Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH 1/2] hung_task: Show the blocker task if the task is
 hung on mutex

On Thu, 20 Feb 2025 08:13:31 -0500
Waiman Long <llong@...hat.com> wrote:

> Another alternative is to encode the locking type into the lowest 2 bits 
> of the address and combined them into a single atomic_long_t data item. 
> Of course, we can only support 4 different types with this scheme.

You could also use the MSB as they are either always all ones or all zeros
depending on the architecture ;-)

-- Steve