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Re: [PATCH] locking/qrwlock: fix write unlock issue in big endian

From Will Deacon <will.deacon@arm.com>
Newsgroups linux.kernel
Subject Re: [PATCH] locking/qrwlock: fix write unlock issue in big endian
Date 2016-06-08 11:30 +0200
Message-ID <rHHYe-6M4-7@gated-at.bofh.it> (permalink)
References <rFxJE-4D3-35@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Thu, Jun 02, 2016 at 06:09:08PM +0800, Pan Xinhui wrote:
> strcut __qrwlock has different layout in big endian machine. we need set
> the __qrwlock->wmode to NULL, and the address is not &lock->cnts in big
> endian machine.
> 
> Do as what read unlock does. we are lucky that the __qrwlock->wmode's
> val is _QW_LOCKED.

Doesn't this have wider implications for the qrwlocks, for example:

  while ((cnts & _QW_WMASK) == _QW_LOCKED) { ... }

would actually end up looking at the wrong field of the lock?

Shouldn't we just remove the #ifdef __LITTLE_ENDIAN stuff from __qrwlock,
given that all the struct members are u8?

Will

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Thread

[PATCH] locking/qrwlock: fix write unlock issue in big endian Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-02 12:10 +0200
  Re: [PATCH] locking/qrwlock: fix write unlock issue in big endian Arnd Bergmann <arnd@arndb.de> - 2016-06-02 12:50 +0200
    Re: [PATCH] locking/qrwlock: fix write unlock issue in big endian xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-02 13:10 +0200
      Re: [PATCH] locking/qrwlock: fix write unlock issue in big endian Peter Zijlstra <peterz@infradead.org> - 2016-06-02 13:20 +0200
        Re: [PATCH] locking/qrwlock: fix write unlock issue in big endian xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-03 09:30 +0200
    Re: [PATCH] locking/qrwlock: fix write unlock issue in big endian Peter Zijlstra <peterz@infradead.org> - 2016-06-02 13:10 +0200
      Re: [PATCH] locking/qrwlock: fix write unlock issue in big endian xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-03 09:20 +0200
      Re: [PATCH] locking/qrwlock: fix write unlock issue in big endian xinhui <xinhui.pan@linux.vnet.ibm.com> - 2016-06-06 05:20 +0200
  Re: [PATCH] locking/qrwlock: fix write unlock issue in big endian Will Deacon <will.deacon@arm.com> - 2016-06-08 11:30 +0200

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