On Friday, September 25, 2015 01:25:49 PM Viresh Kumar wrote:

On 25 September 2015 at 13:33, Rafael J. Wysocki [off-list ref] wrote:

quoted

You're going to change that into bool in the next patch, right?

Yeah.

quoted

So what if bool is a byte and the field is not word-aligned

Its between two 'unsigned long' variables today, and the struct isn't packed.
So, it will be aligned, isn't it?

quoted

and changing
that byte requires a read-modify-write.  How do we ensure that things remain
consistent in that case?

I didn't understood why a read-modify-write is special here? That's
what will happen
to most of the non-word-sized fields anyway?

Probably I didn't understood what you meant..

Say you have three adjacent fields in a structure, x, y, z, each one byte long.
Initially, all of them are equal to 0.

CPU A writes 1 to x and CPU B writes 2 to y at the same time.

What's the result?

Thanks,
Rafael