[LinuxBIOS] PATCH: failure/race in secondary CPU startup

[Steven J. Magnani]

This patch does two things:

* Prints a failure message when a sibling CPU fails to start
  (currently, a message is printed only when a CPU enumerated 
  in Config.lb fails to start).

* Detects a race condition that results in secondary CPUs 
  using the wrong CPU info. This can occur if the BSP times
  out waiting for a secondary CPU to respond, for example
  if the secondary startup code is modified so that an
  emulator can be used to debug the secondary CPU.
  
PATCH:

--- src/cpu/intel/hyperthreading/intel_sibling.c.orig	2005-09-08
13:35:05.578125000 -0500
+++ src/cpu/intel/hyperthreading/intel_sibling.c	2005-09-12
11:24:20.546875000 -0500
@@ -67,7 +67,11 @@
 			new->path.u.apic.apic_id);
 #endif
 		/* Start the new cpu */
-		start_cpu(new);
+		if (!start_cpu(new)) {
+			/* Record the error in cpu? */
+			printk_err("CPU %u would not start!\n",
+				new->path.u.apic.apic_id);
+		}
 	}
 	
 }


--- src/arch/i386/lib/cpu.c.orig	2005-09-08 13:35:40.875000000
-0500
+++ src/arch/i386/lib/cpu.c	2005-09-12 11:26:27.375000000 -0500
@@ -231,6 +231,14 @@
 		die("CPU: missing cpu device structure");
 	}
 
+	// Check that we haven't been passed bad information as the
result of a race 
+	// (i.e. BSP timed out while waiting for us to load
secondary_stack)
+
+	if (cpu->path.u.apic.apic_id != lapicid()) {
+		printk_err("CPU #%d Initialization FAILED: APIC ID
mismatch (%u != %u)\n",
+				   info->index,
cpu->path.u.apic.apic_id, lapicid());
+		// return without setting initialized flag
+	} else {
 	/* Find what type of cpu we are dealing with */
 	identify_cpu(cpu);
 	printk_debug("CPU: vendor %s device %x\n",
@@ -247,6 +255,8 @@
 	}
 
 	printk_info("CPU #%d Initialized\n", info->index);
+	}
+
 	return;
 }
 
------------------------------------------------------------------------
 Steven J. Magnani               "I claim this network for MARS!
 www.digidescorp.com              Earthling, return my space modulator!"
 
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