From: Andy Shevchenko <andriy.shevchenko@linux•intel.com>
To: Bjorn Helgaas <helgaas@kernel•org>, David Howells <dhowells@redhat•com>
Cc: Sam Bobroff <sbobroff@linux•ibm.com>,
linuxppc-dev@lists•ozlabs.org,
Oliver O'Halloran <oohall@gmail•com>,
linux-pci@vger•kernel.org
Subject: Re: [PATCH v1 1/2] PCI/AER: Use for_each_set_bit()
Date: Mon, 30 Sep 2019 15:13:13 +0300 [thread overview]
Message-ID: <20190930121313.GV32742@smile.fi.intel.com> (raw)
In-Reply-To: <20190927123913.GA32321@google.com>
On Fri, Sep 27, 2019 at 07:39:13AM -0500, Bjorn Helgaas wrote:
> On Tue, Aug 27, 2019 at 06:18:22PM +0300, Andy Shevchenko wrote:
> > This simplifies and standardizes slot manipulation code
> > by using for_each_set_bit() library function.
> > + unsigned long status = info->status & ~info->mask;
> > + int i, max = -1;
> > - for (i = 0; i < max; i++)
> > - if (status & (1 << i))
> > - counter[i]++;
> > + for_each_set_bit(i, &status, max)
>
> I applied this,
Thank you!
> but I confess to being a little ambivalent. It's
> arguably a little easier to read,
I have another opinion here. Instead of parsing body of for-loop, the name of
the function tells you exactly what it's done. Besides the fact that reading
and parsing two lines, with zero conditionals, is faster.
> but it's not nearly as efficient
> (not a great concern here)
David, do you know why for_each_set_bit() has no optimization for the cases
when nbits <= BITS_PER_LONG? (Actually find_*bit() family of functions)
> and more importantly much harder to verify
> that it's correct because you have to chase through
> for_each_set_bit(), find_first_bit(), _ffs(), etc, etc.
If for_each_set_bit() or any other fundamental bit operation helper is broken,
PCI subsystem is a little concern here.
> No doubt it's
> great for bitmaps of arbitrary size, but for a simple 32-bit register
> I'm a little hesitant. But I applied it anyway.
>
> > + counter[i]++;
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2019-09-30 12:17 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-27 15:18 [PATCH v1 1/2] PCI/AER: Use for_each_set_bit() Andy Shevchenko
2019-08-27 15:18 ` [PATCH v1 2/2] PCI/AER: Update parameter descriptions to satisfy kernel-doc validator Andy Shevchenko
2019-08-27 17:06 ` Kuppuswamy Sathyanarayanan
2019-08-28 10:07 ` Andy Shevchenko
2019-08-27 17:06 ` [PATCH v1 1/2] PCI/AER: Use for_each_set_bit() Kuppuswamy Sathyanarayanan
2019-09-27 10:44 ` Bjorn Helgaas
2019-09-27 12:39 ` Bjorn Helgaas
2019-09-30 12:13 ` Andy Shevchenko [this message]
2019-10-02 10:27 ` David Howells
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