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-rw-r--r--src/cpu/x86/lapic/lapic_cpu_init.c29
1 files changed, 25 insertions, 4 deletions
diff --git a/src/cpu/x86/lapic/lapic_cpu_init.c b/src/cpu/x86/lapic/lapic_cpu_init.c
index fc22ea4adf..2e2bb0632c 100644
--- a/src/cpu/x86/lapic/lapic_cpu_init.c
+++ b/src/cpu/x86/lapic/lapic_cpu_init.c
@@ -277,6 +277,19 @@ int start_cpu(device_t cpu)
}
#if CONFIG_AP_IN_SIPI_WAIT == 1
+
+/**
+ * Sending INIT IPI to self is equivalent of asserting #INIT with a bit of delay.
+ * An undefined number of instruction cycles will complete. All global locks
+ * must be released before INIT IPI and no printk is allowed after this.
+ * De-asserting INIT IPI is a no-op on later Intel CPUs.
+ *
+ * If you set DEBUG_HALT_SELF to 1, printk's after INIT IPI are enabled
+ * but running thread may halt without releasing the lock and effectively
+ * deadlock other CPUs.
+ */
+#define DEBUG_HALT_SELF 0
+
/**
* Normally this function is defined in lapic.h as an always inline function
* that just keeps the CPU in a hlt() loop. This does not work on all CPUs.
@@ -298,38 +311,46 @@ void stop_this_cpu(void)
lapic_write_around(LAPIC_ICR, LAPIC_INT_LEVELTRIG | LAPIC_INT_ASSERT | LAPIC_DM_INIT);
/* wait for the ipi send to finish */
-#if 0
- // When these two printk(BIOS_SPEW, ...) calls are not removed, the
- // machine will hang when log level is SPEW. Why?
+#if DEBUG_HALT_SELF
printk(BIOS_SPEW, "Waiting for send to finish...\n");
#endif
timeout = 0;
do {
-#if 0
+#if DEBUG_HALT_SELF
printk(BIOS_SPEW, "+");
#endif
udelay(100);
send_status = lapic_read(LAPIC_ICR) & LAPIC_ICR_BUSY;
} while (send_status && (timeout++ < 1000));
if (timeout >= 1000) {
+#if DEBUG_HALT_SELF
printk(BIOS_ERR, "timed out\n");
+#endif
}
mdelay(10);
+#if DEBUG_HALT_SELF
printk(BIOS_SPEW, "Deasserting INIT.\n");
+#endif
/* Deassert the LAPIC INIT */
lapic_write_around(LAPIC_ICR2, SET_LAPIC_DEST_FIELD(id));
lapic_write_around(LAPIC_ICR, LAPIC_INT_LEVELTRIG | LAPIC_DM_INIT);
+#if DEBUG_HALT_SELF
printk(BIOS_SPEW, "Waiting for send to finish...\n");
+#endif
timeout = 0;
do {
+#if DEBUG_HALT_SELF
printk(BIOS_SPEW, "+");
+#endif
udelay(100);
send_status = lapic_read(LAPIC_ICR) & LAPIC_ICR_BUSY;
} while (send_status && (timeout++ < 1000));
if (timeout >= 1000) {
+#if DEBUG_HALT_SELF
printk(BIOS_ERR, "timed out\n");
+#endif
}
while(1) {