Messages in this thread Patch in this message | | | Subject | [PATCH 29 of 31] xen: short-cut for recursive event handling | Date | Mon, 17 Mar 2008 16:37:20 -0700 | From | Jeremy Fitzhardinge <> |
| |
If an event comes in while events are currently being processed, then just increment the counter and have the outer event loop reprocess the pending events. This prevents unbounded recursion on heavy event loads (of course massive event storms will cause infinite loops).
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> --- arch/x86/xen/events.c | 46 ++++++++++++++++++++++++++++++---------------- 1 file changed, 30 insertions(+), 16 deletions(-)
diff --git a/arch/x86/xen/events.c b/arch/x86/xen/events.c --- a/arch/x86/xen/events.c +++ b/arch/x86/xen/events.c @@ -517,29 +517,43 @@ int cpu = get_cpu(); struct shared_info *s = HYPERVISOR_shared_info; struct vcpu_info *vcpu_info = __get_cpu_var(xen_vcpu); - unsigned long pending_words; + static DEFINE_PER_CPU(unsigned, nesting_count); + unsigned count; - vcpu_info->evtchn_upcall_pending = 0; + do { + unsigned long pending_words; - /* NB. No need for a barrier here -- XCHG is a barrier on x86. */ - pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0); - while (pending_words != 0) { - unsigned long pending_bits; - int word_idx = __ffs(pending_words); - pending_words &= ~(1UL << word_idx); + vcpu_info->evtchn_upcall_pending = 0; - while ((pending_bits = active_evtchns(cpu, s, word_idx)) != 0) { - int bit_idx = __ffs(pending_bits); - int port = (word_idx * BITS_PER_LONG) + bit_idx; - int irq = evtchn_to_irq[port]; + if (__get_cpu_var(nesting_count)++) + goto out; - if (irq != -1) { - regs->orig_ax = ~irq; - do_IRQ(regs); + /* NB. No need for a barrier here -- XCHG is a barrier on x86. */ + pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0); + while (pending_words != 0) { + unsigned long pending_bits; + int word_idx = __ffs(pending_words); + pending_words &= ~(1UL << word_idx); + + while ((pending_bits = active_evtchns(cpu, s, word_idx)) != 0) { + int bit_idx = __ffs(pending_bits); + int port = (word_idx * BITS_PER_LONG) + bit_idx; + int irq = evtchn_to_irq[port]; + + if (irq != -1) { + regs->orig_ax = ~irq; + do_IRQ(regs); + } } } - } + BUG_ON(!irqs_disabled()); + + count = __get_cpu_var(nesting_count); + __get_cpu_var(nesting_count) = 0; + } while(count != 1); + +out: put_cpu(); }
| |