linux-kernel - Please correct this code

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Message-ID: <AANLkTinR=GN+rNqAUcFrnUXea0aWmew-wde0oP22uPcj@mail.gmail.com>
Date:	Mon, 31 Jan 2011 11:37:54 -0500
From:	Sri Ram Vemulpali <sri.ram.gmu06@...il.com>
To:	Kernel-newbies <kernelnewbies@...linux.org>,
	linux-kernel-mail <linux-kernel@...r.kernel.org>
Subject: Please correct this code

Hi,

I have following snippet of code.

Code A

__asm__ __volatile__(
                     "   lock       ;\n"
                     "   addl %1,%0 ;\n"
                     : "=m"  (my_var)
                     : "ir"  (my_int), "m" (my_var)
                     :                                 /* no clobber-list */
                     );

Code B

 __asm__ __volatile__(  "decl %0; sete %1"
                     : "=m" (my_var), "=q" (cond)
                     : "m" (my_var)
                     : "memory"
                     );

In Code A memory contents are getting updated. And in Code B memory
contents and 'cond' var are getting updated.
In Code B in cobbler column 'memory' is used to indicate that this
code modifies memory contents. But where as in Code A it was not
mentioned

Is is not that Code A is wrong, for not mentioning cobbler list
'memory' to indicate memory contents are getting updated.
Please rectify me, if I am wrong.

Also, what does '+m' constraint mean, if I use in inline assembly.
--
Regards,
Sri.
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