From: Andreas Schwab <schwab@suse.de>
To: David Laight <david.laight.linux@gmail.com>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv/atomic: Do proper sign extension also for unsigned in arch_cmpxchg
Date: Mon, 03 Feb 2025 09:42:02 +0100 [thread overview]
Message-ID: <mvmseov2zdx.fsf@suse.de> (raw)
In-Reply-To: <20250130213504.285b4675@pumpkin> (David Laight's message of "Thu, 30 Jan 2025 21:35:04 +0000")
On Jan 30 2025, David Laight wrote:
> On Thu, 30 Jan 2025 10:25:38 +0100
> Andreas Schwab <schwab@suse.de> wrote:
>
>> Sign extend also an unsigned compare value to match what lr.w is doing.
>> Otherwise try_cmpxchg may spuriously return true when used on a u32 value
>> that has the sign bit set, as it happens often in inode_set_ctime_current.
>>
>> Do this in three conversion steps. The first conversion to long is needed
>> to avoid a -Wpointer-to-int-cast warning when arch_cmpxchg is used with a
>> pointer type.
>
> Doesn't that break things by discarding the high bits of a pointer value?
If you have 32-bit pointers then the conversions are no-ops.
--
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."
next prev parent reply other threads:[~2025-02-03 8:42 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-30 9:25 [PATCH] riscv/atomic: Do proper sign extension also for unsigned in arch_cmpxchg Andreas Schwab
2025-01-30 14:18 ` Alexandre Ghiti
2025-01-30 14:52 ` Andreas Schwab
2025-01-30 15:23 ` Alexandre Ghiti
2025-01-30 15:53 ` Andreas Schwab
2025-01-30 17:21 ` Jessica Clarke
2025-02-03 8:42 ` Andreas Schwab
2025-02-03 13:57 ` Maciej W. Rozycki
2025-02-03 21:22 ` Jessica Clarke
2025-02-04 16:44 ` Maciej W. Rozycki
2025-01-30 14:40 ` Andrew Jones
2025-01-30 21:35 ` David Laight
2025-02-03 8:42 ` Andreas Schwab [this message]
2025-02-01 12:17 ` Xi Ruoyao
2025-02-04 8:33 ` Alexandre Ghiti
2025-02-13 18:30 ` patchwork-bot+linux-riscv
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