Re: Perf: WARNING: arch/x86/entry/common.c:624 idtentry_exit_cond_rcu+0x92/0xc0

Andy Lutomirski luto@kernel.org writes:

On Thu, Jun 11, 2020 at 4:22 PM Andy Lutomirski luto@kernel.org wrote:

Two bugs here.

1. We had an issue with WARN. Patch sent.

Grabbed it

2. idtentry.h has, for x86_32:

# define DEFINE_IDTENTRY_IST DEFINE_IDTENTRY

This is nonsense. It's getting late over here and I'd rather focus on the more interesting RCU issue, so that's all from me today.

Well, this might be nonsense, but it's exactly matching the current code in mainline which, e.g. for #DB does:

SYM_CODE_START(debug) /* * Entry from sysenter is now handled in common_exception */ ASM_CLAC pushl $0 pushl $do_debug jmp common_exception SYM_CODE_END(debug)

There is no IST on 32bit, never was. We do software stack switching for device interrupts, but that's a different story.

Thanks,

tglx