| David Vrabel | fdfd811 | 2015-02-19 15:23:17 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Preemptible hypercalls |
| 3 | * |
| 4 | * Copyright (C) 2014 Citrix Systems R&D ltd. |
| 5 | * |
| 6 | * This source code is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU General Public License as |
| 8 | * published by the Free Software Foundation; either version 2 of the |
| 9 | * License, or (at your option) any later version. |
| 10 | */ |
| 11 | |
| 12 | #include <linux/sched.h> |
| 13 | #include <xen/xen-ops.h> |
| 14 | |
| 15 | #ifndef CONFIG_PREEMPT |
| 16 | |
| 17 | /* |
| 18 | * Some hypercalls issued by the toolstack can take many 10s of |
| 19 | * seconds. Allow tasks running hypercalls via the privcmd driver to |
| 20 | * be voluntarily preempted even if full kernel preemption is |
| 21 | * disabled. |
| 22 | * |
| 23 | * Such preemptible hypercalls are bracketed by |
| 24 | * xen_preemptible_hcall_begin() and xen_preemptible_hcall_end() |
| 25 | * calls. |
| 26 | */ |
| 27 | |
| 28 | DEFINE_PER_CPU(bool, xen_in_preemptible_hcall); |
| 29 | EXPORT_SYMBOL_GPL(xen_in_preemptible_hcall); |
| 30 | |
| 31 | asmlinkage __visible void xen_maybe_preempt_hcall(void) |
| 32 | { |
| 33 | if (unlikely(__this_cpu_read(xen_in_preemptible_hcall) |
| 34 | && should_resched())) { |
| 35 | /* |
| 36 | * Clear flag as we may be rescheduled on a different |
| 37 | * cpu. |
| 38 | */ |
| 39 | __this_cpu_write(xen_in_preemptible_hcall, false); |
| 40 | _cond_resched(); |
| 41 | __this_cpu_write(xen_in_preemptible_hcall, true); |
| 42 | } |
| 43 | } |
| 44 | #endif /* CONFIG_PREEMPT */ |