On Wed, Sep 14, 2016 at 12:38 PM, Richard Henderson <r...@twiddle.net> wrote: > On 09/14/2016 09:03 AM, Alex Bennée wrote: >>> > -/* Load/Store exclusive instructions are implemented by remembering >>> > - the value/address loaded, and seeing if these are the same >>> > - when the store is performed. This should be sufficient to implement >>> > - the architecturally mandated semantics, and avoids having to monitor >>> > - regular stores. >>> > - >>> > - In system emulation mode only one CPU will be running at once, so >>> > - this sequence is effectively atomic. In user emulation mode we >>> > - throw an exception and handle the atomic operation elsewhere. */ >> At least half of this comment is still relevant although it could be >> tweaked to mention that we use an atomic cmpxchg for the store that will >> fail if exlusive_val doesn't match the current state. >> > > Added back > > /* Load/Store exclusive instructions are implemented by remembering > the value/address loaded, and seeing if these are the same > when the store is performed. This should be sufficient to implement > the architecturally mandated semantics, and avoids having to monitor > regular stores. The compare vs the remembered value is done during > the cmpxchg operation, but we must compare the addresses manually. */ >
FYI, I do not see this in your v7 series. -- Pranith
