[RFC PATCH 09/14] powerpc/tm: Warn if state is transactional

[Michael Neuling]

On Tue, 2018-11-06 at 10:40 -0200, Breno Leitao wrote:
> Since every kernel entrance is calling TM_KERNEL_ENTRY, it is not
> expected to arrive at this point with a suspended transaction.
> 
> If that is the case, cause a warning and reclaim the current thread in
> order to avoid a TM Bad Thing.
> 
> Signed-off-by: Breno Leitao <leitao at debian.org>
> ---
>  arch/powerpc/kernel/process.c | 7 +++----
>  arch/powerpc/kernel/signal.c  | 2 +-
>  2 files changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 73872f751b33..849591bf0881 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1752,11 +1752,10 @@ void start_thread(struct pt_regs *regs, unsigned long
> start, unsigned long sp)
>  
>  #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
>  	/*
> -	 * Clear any transactional state, we're exec()ing. The cause is
> -	 * not important as there will never be a recheckpoint so it's not
> -	 * user visible.
> +	 * It is a bug if the transaction was not reclaimed until this
> +	 * point. Warn us and try to workaround it calling tm_reclaim().
>  	 */
> -	if (MSR_TM_SUSPENDED(mfmsr()))
> +	if (WARN_ON(MSR_TM_SUSPENDED(mfmsr())))
>  		tm_reclaim_current(0);
>  #endif

Let's turn these into BUG_ON()

Mikey
 
> diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
> index b3e8db376ecd..cbaccc2be0fb 100644
> --- a/arch/powerpc/kernel/signal.c
> +++ b/arch/powerpc/kernel/signal.c
> @@ -203,7 +203,7 @@ unsigned long get_tm_stackpointer(struct task_struct *tsk)
>  #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
>  	BUG_ON(tsk != current);
>  
> -	if (MSR_TM_ACTIVE(tsk->thread.regs->msr)) {
> +	if (WARN_ON(MSR_TM_ACTIVE(mfmsr()))) {
>  		tm_reclaim_current(TM_CAUSE_SIGNAL);
>  		if (MSR_TM_TRANSACTIONAL(tsk->thread.regs->msr))
>  			return tsk->thread.ckpt_regs.gpr[1];