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xen: Enable interrupts when calling _cond_resched()

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commit 8645e56a4ad6dcbf504872db7f14a2f67db88ef2 upstream.

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: fdfd811ddd ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Thomas Gleixner 2020-02-19 18:30:26 +01:00 • committed by Greg Kroah-Hartman
parent dfbf241286
commit 1d982f7f03
1 changed files with 3 additions and 1 deletions
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4
drivers/xen/preempt.c
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@ -37,7 +37,9 @@ 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);
}
}