powerpc/64: Drop reservation-clearing ldarx in context switch
authorNicholas Piggin <npiggin@gmail.com>
Thu, 8 Jun 2017 15:36:07 +0000 (01:36 +1000)
committerMichael Ellerman <mpe@ellerman.id.au>
Thu, 15 Jun 2017 06:34:39 +0000 (16:34 +1000)
commit837e72f78a72ef43a0c5e179f3addadb2a225f80
tree4a16400f9dc5667da0e16a4ac9cbf9764773f21d
parente4c0fc5f72bca11432297168338aef46c12793a4
powerpc/64: Drop reservation-clearing ldarx in context switch

There is no need to explicitly break the reservation in _switch,
because we are guaranteed that the context switch path will include a
larx/stcx.

Comment the guarantee and remove the reservation clear from _switch.

This is worth 1-2% in context switch performance.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
arch/powerpc/kernel/entry_64.S