commit 152d523e6307 ("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(). Signed-off-by: Anton Blanchard <[email protected]> Fixes: 152d523e6307 ("powerpc: Create context switch helpers save_sprs() and restore_sprs()") fold --- arch/powerpc/kernel/process.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 58194c3..6f5c392 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -964,14 +964,17 @@ 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 = ¤t->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; -- 2.5.0 _______________________________________________ Linuxppc-dev mailing list [email protected] https://lists.ozlabs.org/listinfo/linuxppc-dev
