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Re: [Xen-devel] [PATCH] xen: Enable interrupts when calling _cond_resched()

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

Fixes: fdfd811ddde3 ("x86/xen: allow privcmd hypercalls to be preempted")
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
  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?


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