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Commit ada6814c authored by Keir Fraser's avatar Keir Fraser Committed by Konrad Rzeszutek Wilk
Browse files

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



Also fixes a couple of boundary cases.

Signed-off-by: default avatarKeir Fraser <keir.fraser@citrix.com>
Signed-off-by: default avatarIan Campbell <ian.campbell@citrix.com>
[ijc: forward ported from linux-2.6.18-xen.hg 988:c88a02a22a05]
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent f1f4a323

drivers/xen/events.c

+20 −24
Original line number Original line Diff line number Diff line
@@ -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());