| Message ID | 87tv3mq1rm.fsf@nanos.tec.linutronix.de (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xen: Enable interrupts when calling _cond_resched() | expand |
On 19.02.20 12:01, Thomas Gleixner wrote: > xen_maybe_preempt_hcall() is called from the exception entry point > xen_do_hypervisor_callback with interrupts disabled. > > _cond_resched() evades the might_sleep() check in cond_resched() which > would have caught that and schedule_debug() unfortunately lacks a check > for irqs_disabled(). > > Enable interrupts around the call and use cond_resched() to catch future > issues. > > Fixes: fdfd811ddde3 ("x86/xen: allow privcmd hypercalls to be preempted") > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > --- > drivers/xen/preempt.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > --- a/drivers/xen/preempt.c > +++ b/drivers/xen/preempt.c > @@ -33,8 +33,10 @@ asmlinkage __visible void xen_maybe_pree > * cpu. > */ > __this_cpu_write(xen_in_preemptible_hcall, false); > - _cond_resched(); > + local_irq_enable(); > + cond_resched(); > __this_cpu_write(xen_in_preemptible_hcall, true); > + local_irq_disable(); Could you please put the call of local_irq_disable() directly after the cond_resched() call to make the result symmetric regarding writing of xen_in_preemptible_hcall and irq enable/disable? Juergen
Jürgen Groß <jgross@suse.com> writes: > On 19.02.20 12:01, Thomas Gleixner wrote: >> xen_maybe_preempt_hcall() is called from the exception entry point >> xen_do_hypervisor_callback with interrupts disabled. >> >> _cond_resched() evades the might_sleep() check in cond_resched() which >> would have caught that and schedule_debug() unfortunately lacks a check >> for irqs_disabled(). >> >> Enable interrupts around the call and use cond_resched() to catch future >> issues. >> >> Fixes: fdfd811ddde3 ("x86/xen: allow privcmd hypercalls to be preempted") >> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> >> --- >> drivers/xen/preempt.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> --- a/drivers/xen/preempt.c >> +++ b/drivers/xen/preempt.c >> @@ -33,8 +33,10 @@ asmlinkage __visible void xen_maybe_pree >> * cpu. >> */ >> __this_cpu_write(xen_in_preemptible_hcall, false); >> - _cond_resched(); >> + local_irq_enable(); >> + cond_resched(); >> __this_cpu_write(xen_in_preemptible_hcall, true); >> + local_irq_disable(); > > Could you please put the call of local_irq_disable() directly after the > cond_resched() call to make the result symmetric regarding writing of > xen_in_preemptible_hcall and irq enable/disable? Darn. Of course does this need to be there. Stupid me, let me resend.
--- a/drivers/xen/preempt.c +++ b/drivers/xen/preempt.c @@ -33,8 +33,10 @@ asmlinkage __visible void xen_maybe_pree * cpu. */ __this_cpu_write(xen_in_preemptible_hcall, false); - _cond_resched(); + local_irq_enable(); + cond_resched(); __this_cpu_write(xen_in_preemptible_hcall, true); + local_irq_disable(); } } #endif /* CONFIG_PREEMPTION */
xen_maybe_preempt_hcall() is called from the exception entry point xen_do_hypervisor_callback with interrupts disabled. _cond_resched() evades the might_sleep() check in cond_resched() which would have caught that and schedule_debug() unfortunately lacks a check for irqs_disabled(). Enable interrupts around the call and use cond_resched() to catch future issues. Fixes: fdfd811ddde3 ("x86/xen: allow privcmd hypercalls to be preempted") Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- drivers/xen/preempt.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)