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

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Message-ID: <20250621210157.J4QMzB0C@linutronix.de>
Date: Sat, 21 Jun 2025 23:01:57 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Calvin Owens <calvin@...nvd.org>
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 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:

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