From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Mario Limonciello <mario.limonciello@amd.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Tony Battersby <tonyb@cybernetics.com>,
Ashok Raj <ashok.raj@linux.intel.com>,
Tony Luck <tony.luck@intel.com>,
Arjan van de Veen <arjan@linux.intel.com>,
Eric Biederman <ebiederm@xmission.com>,
Ashok Raj <ashok.raj@intel.com>
Subject: [patch V2 3/8] x86/smp: Remove pointless wmb() from native_stop_other_cpus()
Date: Tue, 13 Jun 2023 14:17:58 +0200 (CEST) [thread overview]
Message-ID: <20230613121615.762734722@linutronix.de> (raw)
In-Reply-To: <20230613115353.599087484@linutronix.de>
The wmb() after the successfull atomic_cmpxchg() is complete voodoo along
with the comment stating "sync above data before sending IRQ".
There is no "above" data except for the atomic_t stopping_cpu which has
just been acquired. The reboot IPI handler does not check any data and
unconditionally disables the CPU.
Remove this cargo cult barrier.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ashok Raj <ashok.raj@intel.com>
---
arch/x86/kernel/smp.c | 3 ---
1 file changed, 3 deletions(-)
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -174,9 +174,6 @@ static void native_stop_other_cpus(int w
atomic_set(&stop_cpus_count, num_online_cpus() - 1);
- /* sync above data before sending IRQ */
- wmb();
-
apic_send_IPI_allbutself(REBOOT_VECTOR);
/*
next prev parent reply other threads:[~2023-06-13 12:18 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-13 12:17 [patch V2 0/8] x86/smp: Cure stop_other_cpus() and kexec() troubles Thomas Gleixner
2023-06-13 12:17 ` [patch V2 1/8] x86/smp: Make stop_other_cpus() more robust Thomas Gleixner
2023-06-14 19:42 ` Ashok Raj
2023-06-14 19:53 ` Thomas Gleixner
2023-06-14 20:47 ` Ashok Raj
2023-06-14 22:40 ` Thomas Gleixner
2023-06-13 12:17 ` [patch V2 2/8] x86/smp: Dont access non-existing CPUID leaf Thomas Gleixner
2023-06-13 12:17 ` Thomas Gleixner [this message]
2023-06-15 8:58 ` [patch V2 3/8] x86/smp: Remove pointless wmb() from native_stop_other_cpus() Peter Zijlstra
2023-06-15 10:57 ` Thomas Gleixner
2023-06-13 12:17 ` [patch V2 4/8] x86/smp: Acquire stopping_cpu unconditionally Thomas Gleixner
2023-06-15 9:02 ` Peter Zijlstra
2023-06-13 12:18 ` [patch V2 5/8] x86/smp: Use dedicated cache-line for mwait_play_dead() Thomas Gleixner
2023-06-13 12:18 ` [patch V2 6/8] x86/smp: Cure kexec() vs. mwait_play_dead() breakage Thomas Gleixner
2023-06-13 12:18 ` [patch V2 7/8] x86/smp: Split sending INIT IPI out into a helper function Thomas Gleixner
2023-06-13 12:18 ` [patch V2 8/8] x86/smp: Put CPUs into INIT on shutdown if possible Thomas Gleixner
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