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powerpc: Call restore_sprs() before _switch() 

commit 152d523e63 ("powerpc: Create context switch helpers save_sprs()
and restore_sprs()") moved the restore of SPRs after the call to _switch().

There is an issue with this approach - new tasks do not return through
_switch(), they are set up by copy_thread() to directly return through
ret_from_fork() or ret_from_kernel_thread(). This means restore_sprs() is
not getting called for new tasks.

Fix this by moving restore_sprs() before _switch().

Fixes: 152d523e63 ("powerpc: Create context switch helpers save_sprs() and restore_sprs()")
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Anton Blanchard 2015-12-10 20:44:39 +11:00 committed by Michael Ellerman
parent d64d02ce4e
commit 20dbe67062
1 changed files with 9 additions and 6 deletions
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15
arch/powerpc/kernel/process.c
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@ -971,14 +971,17 @@ struct task_struct *__switch_to(struct task_struct *prev,
tm_recheckpoint_new_task(new);
last = _switch(old_thread, new_thread);
/* Need to recalculate these after calling _switch() */
old_thread = &last->thread;
new_thread = &current->thread;
/*
* Call restore_sprs() before calling _switch(). If we move it after
* _switch() then we miss out on calling it for new tasks. The reason
* for this is we manually create a stack frame for new tasks that
* directly returns through ret_from_fork() or
* ret_from_kernel_thread(). See copy_thread() for details.
*/
restore_sprs(old_thread, new_thread);
last = _switch(old_thread, new_thread);
#ifdef CONFIG_PPC_BOOK3S_64
if (current_thread_info()->local_flags & _TLF_LAZY_MMU) {
current_thread_info()->local_flags &= ~_TLF_LAZY_MMU;