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From: Thomas Gleixner <tglx@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@efficios.com>, =?utf-8?Q?Andr=C3=A9?= Almeida
 <andrealmeid@igalia.com>,
 Sebastian Andrzej Siewior <bigeasy@linutronix.de>, Carlos O'Donell
 <carlos@redhat.com>, Florian Weimer <fweimer@redhat.com>, Rich Felker
 <dalias@aerifal.cx>, Torvald Riegel <triegel@redhat.com>, Darren Hart
 <dvhart@infradead.org>, Ingo Molnar <mingo@kernel.org>, Davidlohr Bueso
 <dave@stgolabs.net>, Arnd Bergmann <arnd@arndb.de>, "Liam R . Howlett"
 <Liam.Howlett@oracle.com>, Uros Bizjak <ubizjak@gmail.com>, Thomas
 =?utf-8?Q?Wei=C3=9Fschuh?= <linux@weissschuh.net>
Subject: Re: [patch v2 08/11] futex: Add robust futex unlock IP range
In-Reply-To: <20260320090751.GO3738786@noisy.programming.kicks-ass.net>
References: <20260319225224.853416463@kernel.org>
 <20260319231239.682582451@kernel.org>
 <20260320090751.GO3738786@noisy.programming.kicks-ass.net>
Date: Fri, 20 Mar 2026 13:07:34 +0100
Message-ID: <87se9uk8l5.ffs@tglx>
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On Fri, Mar 20 2026 at 10:07, Peter Zijlstra wrote:

> On Fri, Mar 20, 2026 at 12:24:46AM +0100, Thomas Gleixner wrote:
>>  /**
>> + * struct futex_unlock_cs_range - Range for the VDSO unlock critical section
>> + * @start_ip:	The start IP of the robust futex unlock critical section (inclusive)
>> + * @end_ip:	The end IP of the robust futex unlock critical section (exclusive)
>> + * @pop_size32:	Pending OP pointer size indicator. 0 == 64-bit, 1 == 32-bit
>> + */
>> +struct futex_unlock_cs_range {
>> +	unsigned long	       start_ip;
>> +	unsigned long	       end_ip;
>> +	unsigned int	       pop_size32;
>> +};
>> +
>> +#define FUTEX_ROBUST_MAX_CS_RANGES	2
>
> Would it make sense to write that like:
>
> #define FUTEX_ROBUST_MAX_CS_RANGE (1+IS_ENABLED(CONFIG_COMPAT))
>
> Given you only ever use that second entry when COMPAT?

Indeed!