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

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

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@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();
        }
 }
 #endif /* CONFIG_PREEMPTION */

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