From: David Hildenbrand <david@redhat.com>
To: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: kvm@vger.kernel.org, Thomas Huth <thuth@redhat.com>,
Janosch Frank <frankja@linux.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Sebastian Mitterle <smitterl@redhat.com>,
Halil Pasic <pasic@linux.ibm.com>,
linux-s390@vger.kernel.org
Subject: Re: [kvm-unit-tests PATCH v1 2/2] s390x: firq: floating interrupt test
Date: Thu, 2 Dec 2021 12:26:18 +0100 [thread overview]
Message-ID: <ea6ec055-2682-44b1-2aae-20dfcebf9b85@redhat.com> (raw)
In-Reply-To: <95160439-2aa9-765f-9f06-16952e42a495@redhat.com>
On 02.12.21 12:13, David Hildenbrand wrote:
>>> +static void wait_for_sclp_int(void)
>>> +{
>>> + /* Enable SCLP interrupts on this CPU only. */
>>> + ctl_set_bit(0, CTL0_SERVICE_SIGNAL);
>>> +
>>> + set_flag(1);
>>
>> why not just WRITE_ONCE/READ_ONCE?
>
> Because I shamelessly copied that from s390x/smp.c ;)
Oh, and also because WRITE_ONCE/READ_ONCE are semantically the wrong
thing to use:
"Prevent the compiler from merging or refetching reads or writes. The
compiler is also forbidden from reordering successive instances of
READ_ONCE and WRITE_ONCE"
We need memory barriers to prevent reordering with surrounding code.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-12-02 11:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-02 9:58 [kvm-unit-tests PATCH v1 0/2] s390x: firq: floating interrupt test David Hildenbrand
2021-12-02 9:58 ` [kvm-unit-tests PATCH v1 1/2] s390x: make smp_cpu_setup() return 0 on success David Hildenbrand
2021-12-02 10:30 ` Thomas Huth
2021-12-02 10:33 ` Claudio Imbrenda
2021-12-02 11:28 ` Janosch Frank
2021-12-02 9:58 ` [kvm-unit-tests PATCH v1 2/2] s390x: firq: floating interrupt test David Hildenbrand
2021-12-02 11:01 ` Claudio Imbrenda
2021-12-02 11:13 ` David Hildenbrand
2021-12-02 11:26 ` David Hildenbrand [this message]
2021-12-02 12:07 ` Claudio Imbrenda
2021-12-02 12:24 ` David Hildenbrand
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