Commit 8645e56a authored Feb 19, 2020 by Thomas Gleixner Committed by Boris Ostrovsky Feb 20, 2020

xen: Enable interrupts when calling _cond_resched()



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: fdfd811d ("x86/xen: allow privcmd hypercalls to be preempted")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/878skypjrh.fsf@nanos.tec.linutronix.de


Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

parent 9038ec99

drivers/xen/preempt.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -33,7 +33,9 @@ asmlinkage __visible void xen_maybe_preempt_hcall(void)
		* cpu.
		*/
		__this_cpu_write(xen_in_preemptible_hcall, false);
		_cond_resched();
		local_irq_enable();
		cond_resched();
		local_irq_disable();
		__this_cpu_write(xen_in_preemptible_hcall, true);
		}
		}

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