| Message ID | 1414734657-5004-1-git-send-email-anton@samba.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 808be31426af57af22268ef0fcb42617beb3d15b |
| Delegated to: | Michael Ellerman |
| Headers | show |
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 9caab69..194e46d 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -659,7 +659,13 @@ _GLOBAL(ret_from_except_lite) 3: #endif bl save_nvgprs + /* + * Use a non volatile GPR to save and restore our thread_info flags + * across the call to restore_interrupts. + */ + mr r30,r4 bl restore_interrupts + mr r4,r30 addi r3,r1,STACK_FRAME_OVERHEAD bl do_notify_resume b ret_from_except
Back in 7230c5644188 ("powerpc: Rework lazy-interrupt handling") we added a call out to restore_interrupts() (written in c) before calling do_notify_resume: bl restore_interrupts addi r3,r1,STACK_FRAME_OVERHEAD bl do_notify_resume Unfortunately do_notify_resume takes two arguments, the second one being the thread_info flags: void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags) We do populate r4 (the second argument) earlier, but restore_interrupts() is free to muck it up all it wants. My guess is the gcc compiler gods shone down on us and its register allocator never used r4. Sometimes, rarely, luck is on our side. LLVM on the other hand did trample r4. Signed-off-by: Anton Blanchard <anton@samba.org> Cc: stable@vger.kernel.org --- arch/powerpc/kernel/entry_64.S | 6 ++++++ 1 file changed, 6 insertions(+)