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xen: events: Clean up round-robin evtchn scan.

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Also fixes a couple of boundary cases.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
[ijc: forward ported from linux-2.6.18-xen.hg 988:c88a02a22a05]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Keir Fraser 2011-03-03 10:01:11 +00:00 committed by Konrad Rzeszutek Wilk
parent f1f4a323d4
commit ada6814c87
1 changed files with 20 additions and 24 deletions
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44
drivers/xen/events.c
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@ -1026,8 +1026,8 @@ irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
} }
static DEFINE_PER_CPU(unsigned, xed_nesting_count); static DEFINE_PER_CPU(unsigned, xed_nesting_count);
static DEFINE_PER_CPU(unsigned int, last_word_idx) = { BITS_PER_LONG - 1 }; static DEFINE_PER_CPU(unsigned int, current_word_idx);
static DEFINE_PER_CPU(unsigned int, last_bit_idx) = { BITS_PER_LONG - 1 }; static DEFINE_PER_CPU(unsigned int, current_bit_idx);
/* /*
* Mask out the i least significant bits of w * Mask out the i least significant bits of w
@ -1065,23 +1065,21 @@ static void __xen_evtchn_do_upcall(void)
#endif #endif
pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0); pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);
word_idx = __this_cpu_read(last_word_idx); word_idx = __this_cpu_read(current_word_idx);
bit_idx = __this_cpu_read(last_bit_idx); bit_idx = __this_cpu_read(current_bit_idx);
while (pending_words != 0) { while (pending_words != 0) {
unsigned long pending_bits; unsigned long pending_bits;
unsigned long words; unsigned long words;
word_idx = (word_idx + 1) % BITS_PER_LONG;
words = MASK_LSBS(pending_words, word_idx); words = MASK_LSBS(pending_words, word_idx);
/* /*
* If we masked out all events, wrap around to the * If we masked out all events, wrap to beginning.
* beginning.
*/ */
if (words == 0) { if (words == 0) {
word_idx = BITS_PER_LONG - 1; word_idx = 0;
bit_idx = BITS_PER_LONG - 1; bit_idx = 0;
continue; continue;
} }
word_idx = __ffs(words); word_idx = __ffs(words);
@ -1093,14 +1091,11 @@ static void __xen_evtchn_do_upcall(void)
pending_bits = active_evtchns(cpu, s, word_idx); pending_bits = active_evtchns(cpu, s, word_idx);
bit_idx = (bit_idx + 1) % BITS_PER_LONG;
bits = MASK_LSBS(pending_bits, bit_idx); bits = MASK_LSBS(pending_bits, bit_idx);
/* If we masked out all events, move on. */ /* If we masked out all events, move on. */
if (bits == 0) { if (bits == 0)
bit_idx = BITS_PER_LONG - 1;
break; break;
}
bit_idx = __ffs(bits); bit_idx = __ffs(bits);
@ -1117,22 +1112,23 @@ static void __xen_evtchn_do_upcall(void)
generic_handle_irq_desc(irq, desc); generic_handle_irq_desc(irq, desc);
} }
/* bit_idx = (bit_idx + 1) % BITS_PER_LONG;
* If this is the final port processed, we'll
* pick up here+1 next time. /* Next caller starts at last processed + 1 */
*/ __this_cpu_write(current_word_idx,
__this_cpu_write(last_word_idx, word_idx); bit_idx ? word_idx :
__this_cpu_write(last_bit_idx, bit_idx); (word_idx+1) % BITS_PER_LONG);
} while (bit_idx != BITS_PER_LONG - 1); __this_cpu_write(current_bit_idx, bit_idx);
} while (bit_idx != 0);
pending_bits = active_evtchns(cpu, s, word_idx); pending_bits = active_evtchns(cpu, s, word_idx);
/* /* If we handled all ports, clear the selector bit. */
* We handled all ports, so we can clear the
* selector bit.
*/
if (pending_bits == 0) if (pending_bits == 0)
pending_words &= ~(1UL << word_idx); pending_words &= ~(1UL << word_idx);
word_idx = (word_idx + 1) % BITS_PER_LONG;
bit_idx = 0;
} }
BUG_ON(!irqs_disabled()); BUG_ON(!irqs_disabled());