diff options
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/xen/Makefile | 2 | ||||
| -rw-r--r-- | drivers/xen/preempt.c | 44 | ||||
| -rw-r--r-- | drivers/xen/privcmd.c | 2 |
3 files changed, 47 insertions, 1 deletions
diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile index 2140398a2a8c..2ccd3592d41f 100644 --- a/drivers/xen/Makefile +++ b/drivers/xen/Makefile @@ -2,7 +2,7 @@ ifeq ($(filter y, $(CONFIG_ARM) $(CONFIG_ARM64)),) obj-$(CONFIG_HOTPLUG_CPU) += cpu_hotplug.o endif obj-$(CONFIG_X86) += fallback.o -obj-y += grant-table.o features.o balloon.o manage.o +obj-y += grant-table.o features.o balloon.o manage.o preempt.o obj-y += events/ obj-y += xenbus/ diff --git a/drivers/xen/preempt.c b/drivers/xen/preempt.c new file mode 100644 index 000000000000..a1800c150839 --- /dev/null +++ b/drivers/xen/preempt.c @@ -0,0 +1,44 @@ +/* + * 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) + && should_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 */ diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c index 569a13b9e856..59ac71c4a043 100644 --- a/drivers/xen/privcmd.c +++ b/drivers/xen/privcmd.c @@ -56,10 +56,12 @@ static long privcmd_ioctl_hypercall(void __user *udata) if (copy_from_user(&hypercall, udata, sizeof(hypercall))) return -EFAULT; + xen_preemptible_hcall_begin(); ret = privcmd_call(hypercall.op, hypercall.arg[0], hypercall.arg[1], hypercall.arg[2], hypercall.arg[3], hypercall.arg[4]); + xen_preemptible_hcall_end(); return ret; } |