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authorJuergen Gross <jgross@suse.com>2023-10-24 13:51:36 +0200
committerJuergen Gross <jgross@suse.com>2023-11-13 07:22:00 +0100
commite64e7c74b99ec9e439abca75f522f4b98f220bd1 (patch)
treebf1beaabc09842d03aa36ae4307e3ec00d7620d6
parentb85ea95d086471afb4ad062012a4d73cd328fa86 (diff)
xen/events: avoid using info_for_irq() in xen_send_IPI_one()
xen_send_IPI_one() is being used by cpuhp_report_idle_dead() after it calls rcu_report_dead(), meaning that any RCU usage by xen_send_IPI_one() is a bad idea. Unfortunately xen_send_IPI_one() is using notify_remote_via_irq() today, which is using irq_get_chip_data() via info_for_irq(). And irq_get_chip_data() in turn is using a maple-tree lookup requiring RCU. Avoid this problem by caching the ipi event channels in another percpu variable, allowing the use notify_remote_via_evtchn() in xen_send_IPI_one(). Fixes: 721255b9826b ("genirq: Use a maple tree for interrupt descriptor management") Reported-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Juergen Gross <jgross@suse.com> Tested-by: David Woodhouse <dwmw@amazon.co.uk> Acked-by: Stefano Stabellini <sstabellini@kernel.org> Signed-off-by: Juergen Gross <jgross@suse.com>
-rw-r--r--drivers/xen/events/events_base.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index 6de6b084ea60..237e6b884f72 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -164,6 +164,8 @@ static DEFINE_PER_CPU(int [NR_VIRQS], virq_to_irq) = {[0 ... NR_VIRQS-1] = -1};
/* IRQ <-> IPI mapping */
static DEFINE_PER_CPU(int [XEN_NR_IPIS], ipi_to_irq) = {[0 ... XEN_NR_IPIS-1] = -1};
+/* Cache for IPI event channels - needed for hot cpu unplug (avoid RCU usage). */
+static DEFINE_PER_CPU(evtchn_port_t [XEN_NR_IPIS], ipi_to_evtchn) = {[0 ... XEN_NR_IPIS-1] = 0};
/* Event channel distribution data */
static atomic_t channels_on_cpu[NR_CPUS];
@@ -366,6 +368,7 @@ static int xen_irq_info_ipi_setup(unsigned cpu,
info->u.ipi = ipi;
per_cpu(ipi_to_irq, cpu)[ipi] = irq;
+ per_cpu(ipi_to_evtchn, cpu)[ipi] = evtchn;
return xen_irq_info_common_setup(info, irq, IRQT_IPI, evtchn, 0);
}
@@ -981,6 +984,7 @@ static void __unbind_from_irq(unsigned int irq)
break;
case IRQT_IPI:
per_cpu(ipi_to_irq, cpu)[ipi_from_irq(irq)] = -1;
+ per_cpu(ipi_to_evtchn, cpu)[ipi_from_irq(irq)] = 0;
break;
case IRQT_EVTCHN:
dev = info->u.interdomain;
@@ -1632,7 +1636,7 @@ EXPORT_SYMBOL_GPL(evtchn_put);
void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
{
- int irq;
+ evtchn_port_t evtchn;
#ifdef CONFIG_X86
if (unlikely(vector == XEN_NMI_VECTOR)) {
@@ -1643,9 +1647,9 @@ void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
return;
}
#endif
- irq = per_cpu(ipi_to_irq, cpu)[vector];
- BUG_ON(irq < 0);
- notify_remote_via_irq(irq);
+ evtchn = per_cpu(ipi_to_evtchn, cpu)[vector];
+ BUG_ON(evtchn == 0);
+ notify_remote_via_evtchn(evtchn);
}
struct evtchn_loop_ctrl {