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5fca9e5c | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
fdfd811d DV |
2 | /* |
3 | * Preemptible hypercalls | |
4 | * | |
5 | * Copyright (C) 2014 Citrix Systems R&D ltd. | |
fdfd811d DV |
6 | */ |
7 | ||
8 | #include <linux/sched.h> | |
9 | #include <xen/xen-ops.h> | |
10 | ||
11 | #ifndef CONFIG_PREEMPT | |
12 | ||
13 | /* | |
14 | * Some hypercalls issued by the toolstack can take many 10s of | |
15 | * seconds. Allow tasks running hypercalls via the privcmd driver to | |
16 | * be voluntarily preempted even if full kernel preemption is | |
17 | * disabled. | |
18 | * | |
19 | * Such preemptible hypercalls are bracketed by | |
20 | * xen_preemptible_hcall_begin() and xen_preemptible_hcall_end() | |
21 | * calls. | |
22 | */ | |
23 | ||
24 | DEFINE_PER_CPU(bool, xen_in_preemptible_hcall); | |
25 | EXPORT_SYMBOL_GPL(xen_in_preemptible_hcall); | |
26 | ||
27 | asmlinkage __visible void xen_maybe_preempt_hcall(void) | |
28 | { | |
29 | if (unlikely(__this_cpu_read(xen_in_preemptible_hcall) | |
0fa2f5cb | 30 | && need_resched())) { |
fdfd811d DV |
31 | /* |
32 | * Clear flag as we may be rescheduled on a different | |
33 | * cpu. | |
34 | */ | |
35 | __this_cpu_write(xen_in_preemptible_hcall, false); | |
36 | _cond_resched(); | |
37 | __this_cpu_write(xen_in_preemptible_hcall, true); | |
38 | } | |
39 | } | |
40 | #endif /* CONFIG_PREEMPT */ |