projects / linux-2.6-block.git / blame
| Commit | Line | Data |
|---|---|---|
| fdfd811d DV |
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) | |
| 0fa2f5cb | 34 | && need_resched())) { |
| fdfd811d DV |
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 */ |