[PATCH 2/2] ARM: domains: add memory dependencies to get_domain/set_domain

On Fri, Sep 11, 2015 at 04:56:27PM +0200, Robert Jarzmik wrote:

Russell King [off-list ref] writes:

quoted

We need to have memory dependencies on get_domain/set_domain to avoid
the compiler over-optimising these inline assembly instructions.

Loads/stores must not be reordered across a set_domain(), so introduce
a compiler barrier for that assembly.

The value of get_domain() must not be cached across a set_domain(), but
we still want to allow the compiler to optimise it away.  Introduce a
dependency on current_thread_info()->cpu_domain to avoid this; the new
memory clobber in set_domain() should therefore cause the compiler to
re-load this.  The other advantage of using this is we should have its
address in the register set already, or very soon after at most call
sites.

Signed-off-by: Russell King <redacted>

Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>

The test is failing without these 2 patches, while with them, an unaligned
access is fixed, and the generated code looks good :
     7ac:       ee13cf10        mrc     15, 0, ip, cr3, cr0, {0}
     7b0:       e3cc300c        bic     r3, ip, #12
     7b4:       e58dc014        str     ip, [sp, #20]
     7b8:       e3833004        orr     r3, r3, #4
     7bc:       ee033f10        mcr     15, 0, r3, cr3, cr0, {0}

Thanks Robert, I've queued these as fixes now.

If you want to put the bug alignment patch in the patch system, I'll get
that off to Linus this weekend too.

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