Messages in this thread | | | From | Jürgen Groß <> | Subject | Re: [PATCH v2 05/12] x86: rework arch_local_irq_restore() to not use popf | Date | Mon, 23 Nov 2020 06:21:56 +0100 |
| |
On 22.11.20 22:44, Andy Lutomirski wrote: > On Sat, Nov 21, 2020 at 10:55 PM Jürgen Groß <jgross@suse.com> wrote: >> >> On 20.11.20 12:59, Peter Zijlstra wrote: >>> On Fri, Nov 20, 2020 at 12:46:23PM +0100, Juergen Gross wrote: >>>> +static __always_inline void arch_local_irq_restore(unsigned long flags) >>>> +{ >>>> + if (!arch_irqs_disabled_flags(flags)) >>>> + arch_local_irq_enable(); >>>> +} >>> >>> If someone were to write horrible code like: >>> >>> local_irq_disable(); >>> local_irq_save(flags); >>> local_irq_enable(); >>> local_irq_restore(flags); >>> >>> we'd be up some creek without a paddle... now I don't _think_ we have >>> genius code like that, but I'd feel saver if we can haz an assertion in >>> there somewhere... >>> >>> Maybe something like: >>> >>> #ifdef CONFIG_DEBUG_ENTRY // for lack of something saner >>> WARN_ON_ONCE((arch_local_save_flags() ^ flags) & X86_EFLAGS_IF); >>> #endif >>> >>> At the end? >> >> I'd like to, but using WARN_ON_ONCE() in include/asm/irqflags.h sounds >> like a perfect receipt for include dependency hell. >> >> We could use a plain asm("ud2") instead. > > How about out-of-lining it: > > #ifdef CONFIG_DEBUG_ENTRY > extern void warn_bogus_irqrestore(); > #endif > > static __always_inline void arch_local_irq_restore(unsigned long flags) > { > if (!arch_irqs_disabled_flags(flags)) { > arch_local_irq_enable(); > } else { > #ifdef CONFIG_DEBUG_ENTRY > if (unlikely(arch_local_irq_save() & X86_EFLAGS_IF)) > warn_bogus_irqrestore(); > #endif > } >
This couldn't be a WARN_ON_ONCE() then (or it would be a catch all). Another approach might be to open-code the WARN_ON_ONCE(), like:
#ifdef CONFIG_DEBUG_ENTRY extern void warn_bogus_irqrestore(bool *once); #endif
static __always_inline void arch_local_irq_restore(unsigned long flags) { if (!arch_irqs_disabled_flags(flags)) arch_local_irq_enable(); #ifdef CONFIG_DEBUG_ENTRY { static bool once;
if (unlikely(arch_local_irq_save() & X86_EFLAGS_IF)) warn_bogus_irqrestore(&once); } #endif }
Juergen [unhandled content-type:application/pgp-keys][unhandled content-type:application/pgp-signature] | |