tree 02bc288a2692d60e06c216db9b7fed78b3df5ef4
parent 3cee070a13b141b8eb5727c3bfa9920092f87264
author Cyril Bur <cyrilbur@gmail.com> 1474611491 +1000
committer Michael Ellerman <mpe@ellerman.id.au> 1475559787 +1100

powerpc: Never giveup a reclaimed thread when enabling kernel {fp, altivec, vsx}

After a thread is reclaimed from its active or suspended transactional
state the checkpointed state exists on CPU, this state (along with the
live/transactional state) has been saved in its entirety by the
reclaiming process.

There exists a sequence of events that would cause the kernel to call
one of enable_kernel_fp(), enable_kernel_altivec() or
enable_kernel_vsx() after a thread has been reclaimed. These functions
save away any user state on the CPU so that the kernel can use the
registers. Not only is this saving away unnecessary at this point, it
is actually incorrect. It causes a save of the checkpointed state to
the live structures within the thread struct thus destroying the true
live state for that thread.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>