@@ -29,6 +29,7 @@ static void __do_softirq(unsigned long ignore_mask)
{
unsigned int i, cpu;
unsigned long pending;
+ bool rcu_allowed = !(ignore_mask & (1ul << RCU_SOFTIRQ));
for ( ; ; )
{
@@ -38,7 +39,7 @@ static void __do_softirq(unsigned long ignore_mask)
*/
cpu = smp_processor_id();
- if ( rcu_pending(cpu) )
+ if ( rcu_allowed && rcu_pending(cpu) )
rcu_check_callbacks(cpu);
if ( ((pending = (softirq_pending(cpu) & ~ignore_mask)) == 0)
@@ -53,9 +54,16 @@ static void __do_softirq(unsigned long ignore_mask)
void process_pending_softirqs(void)
{
+ unsigned long ignore_mask = (1ul << SCHEDULE_SOFTIRQ) |
+ (1ul << SCHED_SLAVE_SOFTIRQ);
+
+ /* Block RCU processing in case of rcu_read_lock() held. */
+ if ( preempt_count() )
+ ignore_mask |= 1ul << RCU_SOFTIRQ;
+
ASSERT(!in_irq() && local_irq_is_enabled());
/* Do not enter scheduler as it can preempt the calling context. */
- __do_softirq((1ul << SCHEDULE_SOFTIRQ) | (1ul << SCHED_SLAVE_SOFTIRQ));
+ __do_softirq(ignore_mask);
}
void do_softirq(void)
Some keyhandlers are calling process_pending_softirqs() while holding a rcu_read_lock(). This is wrong, as process_pending_softirqs() might activate rcu calls which should not happen inside a rcu_read_lock(). For that purpose modify process_pending_softirqs() to not allow rcu callback processing when a rcu_read_lock() is being held. Signed-off-by: Juergen Gross <jgross@suse.com> --- V3: - add RCU_SOFTIRQ to ignore in process_pending_softirqs_norcu() (Roger Pau Monné) V5: - block rcu processing depending on rch_read_lock() being held or not (Jan Beulich) --- xen/common/softirq.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)