On Mon, 4 Jan 2010 16:52:25 +0100 Oleg Nesterov <oleg@xxxxxxxxxx> wrote: > Hi! > > We have some strange problems with utrace on s390, and so far this _looks_ > like a s390 problem. > > Looks like, on any CPU user_enable_single_step() does not "work" until at > least one thread with per_info.single_step = 1 does the context switch. > > This doesn't matter with the old ptrace implementation, but with utrace > the tracee itself does user_enable_single_step(current) and returns to > user-mode. Until it does at least one context switch the single-stepping > doesn't work, after that everything works fine till the next reboot. The PER control registers only get reloaded on task switch. Can you test if this patch fixes your problem? -- Subject: [PATCH] fix loading of PER control registers for utrace. From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> If the current task enables / disables PER tracing for itself the PER control registers need to be loaded in FixPerRegisters. Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> --- arch/s390/kernel/ptrace.c | 3 +++ 1 file changed, 3 insertions(+) --- a/arch/s390/kernel/ptrace.c +++ b/arch/s390/kernel/ptrace.c @@ -98,6 +98,9 @@ FixPerRegisters(struct task_struct *task per_info->control_regs.bits.storage_alt_space_ctl = 1; else per_info->control_regs.bits.storage_alt_space_ctl = 0; + + if (task == current) + __ctl_load(per_info->control_regs.words, 9, 11); } void user_enable_single_step(struct task_struct *task) -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
