linux-kernel - Re: [tip: locking/urgent] futex: Allow to resize the private local hash

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Message-ID: <aFgsmQQR6MVJNrAO@mozart.vkv.me>
Date: Sun, 22 Jun 2025 09:17:29 -0700
From: Calvin Owens <calvin@...nvd.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: linux-kernel@...r.kernel.org, "Lai, Yi" <yi1.lai@...ux.intel.com>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org
Subject: Re: [tip: locking/urgent] futex: Allow to resize the private local
 hash

On Saturday 06/21 at 23:01 +0200, Sebastian Andrzej Siewior wrote:
> On 2025-06-21 00:24:14 [-0700], Calvin Owens wrote:
> > 
> > I went back to the original GCC config, and set up yocto to log what it
> > was doing over /dev/kmsg so maybe we can isolate the trigger.
> > 
> > I got a novel oops this time:
> 
> I think I got it:
> 
> Could you please try this:

That did it!

Tested-By: Calvin Owens <calvin@...nvd.org>

This was a fun little diversion, thanks :)

> diff --git a/include/linux/futex.h b/include/linux/futex.h
> index 005b040c4791b..b37193653e6b5 100644
> --- a/include/linux/futex.h
> +++ b/include/linux/futex.h
> @@ -89,6 +89,7 @@ void futex_hash_free(struct mm_struct *mm);
>  static inline void futex_mm_init(struct mm_struct *mm)
>  {
>  	RCU_INIT_POINTER(mm->futex_phash, NULL);
> +	mm->futex_phash_new = NULL;
>  	mutex_init(&mm->futex_hash_lock);
>  }
>  
> 
> Sebastian