forked from luck/tmp_suning_uos_patched
0fa2f5cb2b
This code is used only when CONFIG_PREEMPT=n and only in non-atomic context: xen_in_preemptible_hcall is set only in privcmd_ioctl_hypercall(). Thus preempt_count is zero and should_resched() is equal to need_resched(). Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Graf <agraf@suse.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150715095201.12246.49283.stgit@buzz Signed-off-by: Ingo Molnar <mingo@kernel.org>
45 lines
1.2 KiB
C
45 lines
1.2 KiB
C
/*
|
|
* Preemptible hypercalls
|
|
*
|
|
* Copyright (C) 2014 Citrix Systems R&D ltd.
|
|
*
|
|
* This source code is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License as
|
|
* published by the Free Software Foundation; either version 2 of the
|
|
* License, or (at your option) any later version.
|
|
*/
|
|
|
|
#include <linux/sched.h>
|
|
#include <xen/xen-ops.h>
|
|
|
|
#ifndef CONFIG_PREEMPT
|
|
|
|
/*
|
|
* Some hypercalls issued by the toolstack can take many 10s of
|
|
* seconds. Allow tasks running hypercalls via the privcmd driver to
|
|
* be voluntarily preempted even if full kernel preemption is
|
|
* disabled.
|
|
*
|
|
* Such preemptible hypercalls are bracketed by
|
|
* xen_preemptible_hcall_begin() and xen_preemptible_hcall_end()
|
|
* calls.
|
|
*/
|
|
|
|
DEFINE_PER_CPU(bool, xen_in_preemptible_hcall);
|
|
EXPORT_SYMBOL_GPL(xen_in_preemptible_hcall);
|
|
|
|
asmlinkage __visible void xen_maybe_preempt_hcall(void)
|
|
{
|
|
if (unlikely(__this_cpu_read(xen_in_preemptible_hcall)
|
|
&& need_resched())) {
|
|
/*
|
|
* Clear flag as we may be rescheduled on a different
|
|
* cpu.
|
|
*/
|
|
__this_cpu_write(xen_in_preemptible_hcall, false);
|
|
_cond_resched();
|
|
__this_cpu_write(xen_in_preemptible_hcall, true);
|
|
}
|
|
}
|
|
#endif /* CONFIG_PREEMPT */
|