From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Ashok Raj <ashok.raj@linux.intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Tony Luck <tony.luck@intel.com>,
Arjan van de Veen <arjan@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Eric Biederman <ebiederm@xmission.com>
Subject: [patch 1/6] x86/smp: Remove pointless wmb() from native_stop_other_cpus()
Date: Sat, 3 Jun 2023 22:06:56 +0200 (CEST) [thread overview]
Message-ID: <20230603200459.657036052@linutronix.de> (raw)
In-Reply-To: <20230603193439.502645149@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>
---
arch/x86/kernel/smp.c | 3 ---
1 file changed, 3 deletions(-)
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -171,9 +171,6 @@ static void native_stop_other_cpus(int w
if (atomic_cmpxchg(&stopping_cpu, -1, safe_smp_processor_id()) != -1)
return;
- /* sync above data before sending IRQ */
- wmb();
-
apic_send_IPI_allbutself(REBOOT_VECTOR);
/*
next prev parent reply other threads:[~2023-06-03 20:08 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-03 20:06 [patch 0/6] Cure kexec() vs. mwait_play_dead() troubles Thomas Gleixner
2023-06-03 20:06 ` Thomas Gleixner [this message]
2023-06-03 20:06 ` [patch 2/6] x86/smp: Acquire stopping_cpu unconditionally Thomas Gleixner
2023-06-03 20:07 ` [patch 3/6] x86/smp: Use dedicated cache-line for mwait_play_dead() Thomas Gleixner
2023-06-03 20:07 ` [patch 4/6] x86/smp: Cure kexec() vs. mwait_play_dead() breakage Thomas Gleixner
2023-06-03 20:54 ` Ashok Raj
2023-06-04 3:19 ` Ashok Raj
2023-06-05 7:41 ` Thomas Gleixner
2023-06-03 20:07 ` [patch 5/6] x86/smp: Split sending INIT IPI out into a helper function Thomas Gleixner
2023-06-04 4:02 ` Mika Penttilä
2023-06-04 10:24 ` Ashok Raj
2023-06-05 7:54 ` Thomas Gleixner
2023-06-05 8:23 ` [patch v2 " Thomas Gleixner
2023-06-03 20:07 ` [patch 6/6] x86/smp: Put CPUs into INIT on shutdown if possible Thomas Gleixner
2023-06-03 20:57 ` Ashok Raj
2023-06-05 17:41 ` [patch 0/6] Cure kexec() vs. mwait_play_dead() troubles Sean Christopherson
2023-06-05 22:41 ` Thomas Gleixner
2023-06-05 23:08 ` Sean Christopherson
2023-06-06 7:20 ` Thomas Gleixner
2023-06-07 16:21 ` Ashok Raj
2023-06-07 17:33 ` Sean Christopherson
2023-06-07 22:19 ` Ashok Raj
2023-06-08 3:46 ` Sean Christopherson
2023-06-08 4:03 ` Ashok Raj
2023-06-16 15:07 ` Ashok Raj
2023-06-16 19:00 ` Sean Christopherson
2023-06-16 19:03 ` Ashok Raj
2023-06-16 19:08 ` Sean Christopherson
2023-06-09 8:40 ` Paolo Bonzini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20230603200459.657036052@linutronix.de \
--to=tglx@linutronix.de \
--cc=arjan@linux.intel.com \
--cc=ashok.raj@linux.intel.com \
--cc=dave.hansen@linux.intel.com \
--cc=ebiederm@xmission.com \
--cc=linux-kernel@vger.kernel.org \
--cc=peterz@infradead.org \
--cc=tony.luck@intel.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
Powered by JetHome