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Message-id: <451890683.5597891444100921604.JavaMail.weblogic@epmlwas01d> Date: Tue, 06 Oct 2015 03:08:44 +0000 (GMT) From: Sarbojit Ganguly <ganguly.s@...sung.com> To: Will Deacon <will.deacon@....com>, Sarbojit Ganguly <ganguly.s@...sung.com> Cc: "linux@....linux.org.uk" <linux@....linux.org.uk>, "catalin.marinas@....com" <catalin.marinas@....com>, "Waiman.Long@...com" <Waiman.Long@...com>, "peterz@...radead.org" <peterz@...radead.org>, VIKRAM MUPPARTHI <vikram.m@...sung.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, SUNEEL KUMAR SURIMANI <suneel@...sung.com>, SHARAN ALLUR <sharan.allur@...sung.com>, "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org> Subject: Re: Re: Re: [PATCH v2] arm: Adding support for atomic half word exchange Hello Will, Thank you so much for the review. I have thought it over and it makes sense not to have that comment in cmpxchg.h, I will also change !defined to #ifndef and quickly post a v3. Regards, Sarbojit ------- Original Message ------- Sender : Will Deacon<will.deacon@....com> Date : Oct 05, 2015 21:30 (GMT+05:30) Title : Re: Re: [PATCH v2] arm: Adding support for atomic half word exchange On Mon, Oct 05, 2015 at 01:10:53PM +0000, Sarbojit Ganguly wrote: > My sincere apologies for the format issue. This was due to the e-mail editor > which reformats the text. > I am reposting the patch, please let me know if it is ok this time. > > > v1-->v2 : Extended the guard code to cover the byte exchange case as > well following opinion of Will Deacon. > Checkpatch has been run and issues were taken care of. > > Since support for half-word atomic exchange was not there and Qspinlock > on ARM requires it, modified __xchg() to add support for that as well. > ARMv6 and lower does not support ldrex{b,h} so, added a guard code > to prevent build breaks. > > Signed-off-by: Sarbojit Ganguly > --- > arch/arm/include/asm/cmpxchg.h | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h > index 916a274..a53cbeb 100644 > --- a/arch/arm/include/asm/cmpxchg.h > +++ b/arch/arm/include/asm/cmpxchg.h > @@ -39,6 +39,7 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size > > switch (size) { > #if __LINUX_ARM_ARCH__ >= 6 > +#if !defined(CONFIG_CPU_V6) #ifndef ? (to match the __cmpxchg code). > case 1: > asm volatile("@ __xchg1\n" > "1: ldrexb %0, [%3]\n" > @@ -49,6 +50,22 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size > : "r" (x), "r" (ptr) > : "memory", "cc"); > break; > + > + /* > + * Half-word atomic exchange, required > + * for Qspinlock support on ARM. > + */ I think I said it before, but I don't think this comment is of any real value. Other than those, this looks ok to me. Will ????? ??? ?? ?? ?? ----------------------------------------------------------------------+ The Tao lies beyond Yin and Yang. It is silent and still as a pool of water. | It does not seek fame, therefore nobody knows its presence. | It does not seek fortune, for it is complete within itself. | It exists beyond space and time. | ----------------------------------------------------------------------+
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