[Crash-utility] [RFC][PATCH]: crash aborts with cannot determine idle task

[Chandru]

On Friday 12 June 2009 18:06:38 Dave Anderson wrote:
> 
> Yes they will -- I just wanted your sign-off before I checked them in.

Hello Dave,
thanks, here sending the patch again. thanks!

kdump installs NT_PRSTATUS notes into vmcore file only to the cpus that were
online at the time of crash. In such cases, while reading in the notes from the
dump file, we are unsure of the cpu to NT_PRSTATUS  mapping. The cpu
possible, present and online map is not available until cpu_maps_init() initializes
them. Hence we remap the prstatus pointer array to online cpus  before making
any reference to the prstatus information.


Signed-off-by: Chandru Siddalingappa <chandru at linux.vnet.ibm.com>
Signed-off-by: Dave Anderson <anderson at redhat.com>
Reviewed-by: Dave Anderson <anderson at redhat.com>
Cc: Haren Myneni <haren at us.ibm.com>
---

--- crash-4.0-8.10/ppc64.c.orig	2009-06-15 11:47:35.000000000 +0530
+++ crash-4.0-8.10/ppc64.c	2009-06-15 11:59:27.000000000 +0530
@@ -2407,13 +2407,16 @@ ppc64_paca_init(void)
 	if (!symbol_exists("paca"))
 		error(FATAL, "PPC64: Could not find 'paca' symbol\n");
 
-	if (cpu_map_addr("present"))
+	if (cpu_map_addr("possible"))
+		map = POSSIBLE;
+	else if (cpu_map_addr("present"))
 		map = PRESENT;
 	else if (cpu_map_addr("online"))
 		map = ONLINE;
 	else
 		error(FATAL, 
-		    "PPC64: cannot find 'cpu_present_map' or 'cpu_online_map' symbols\n");
+		    "PPC64: cannot find 'cpu_possible_map' or 'cpu_present_map'\
+			or 'cpu_online_map' symbols\n");
 
 	if (!MEMBER_EXISTS("paca_struct", "data_offset"))
 		return;
@@ -2424,7 +2427,7 @@ ppc64_paca_init(void)
 	cpu_paca_buf = GETBUF(SIZE(ppc64_paca));
 
 	if (!(nr_paca = get_array_length("paca", NULL, 0))) 
-		nr_paca = NR_CPUS;
+		nr_paca = (kt->kernel_NR_CPUS ? kt->kernel_NR_CPUS : NR_CPUS);
 
 	if (nr_paca > NR_CPUS) {
 		error(WARNING, 
@@ -2435,7 +2438,7 @@ ppc64_paca_init(void)
 	
 	for (i = cpus = 0; i < nr_paca; i++) {
 		/*
-		 * CPU present (or online)?
+		 * CPU present or online or can exist in the system(possible)?
 		 */
 		if (!in_cpu_map(map, i))
 			continue;
--- crash-4.0-8.10/task.c.orig	2009-06-15 11:47:29.000000000 +0530
+++ crash-4.0-8.10/task.c	2009-06-15 11:53:48.000000000 +0530
@@ -452,6 +452,8 @@ task_init(void)
 		tt->this_task = pid_to_task(active_pid);
 	}
 	else {
+		if (KDUMP_DUMPFILE())
+			map_cpus_to_prstatus();
 		please_wait("determining panic task");
 		set_context(get_panic_context(), NO_PID);
 		please_wait_done();
--- crash-4.0-8.10/netdump.c.orig	2009-06-15 11:47:25.000000000 +0530
+++ crash-4.0-8.10/netdump.c	2009-06-15 12:03:00.000000000 +0530
@@ -45,6 +45,44 @@ static void check_dumpfile_size(char *);
 	(machine_type("IA64") || machine_type("PPC64"))
 
 /*
+ * kdump installs NT_PRSTATUS elf notes only to the cpus
+ * that were online during dumping. Hence we call into this
+ * function to remap the NT_PRSTATUS notes only to the online cpus
+ */
+void
+map_cpus_to_prstatus(void)
+{
+	void **nt_ptr;
+	int online, i, j, nrcpus;
+	size_t size;
+
+	if (!(online = get_cpus_online()) || (online == kt->cpus))
+		return;
+
+	if (CRASHDEBUG(1))
+		error(INFO,
+		    "cpus: %d online: %d NT_PRSTATUS notes: %d (remapping)\n",
+			kt->cpus, online, nd->num_prstatus_notes);
+
+	size = NR_CPUS * sizeof(void *);
+
+	nt_ptr = (void **)GETBUF(size);
+	BCOPY(nd->nt_prstatus_percpu, nt_ptr, size);
+	BZERO(nd->nt_prstatus_percpu, size);
+
+	/*
+	 *  Re-populate the array with the notes mapping to online cpus
+	 */
+	nrcpus = (kt->kernel_NR_CPUS ? kt->kernel_NR_CPUS : NR_CPUS);
+
+	for (i = 0, j = 0; i < nrcpus; i++) {
+		if (in_cpu_map(ONLINE, i))
+			nd->nt_prstatus_percpu[i] = nt_ptr[j++];
+	}
+
+	FREEBUF(nt_ptr);
+}
+/*
  *  Determine whether a file is a netdump/diskdump/kdump creation, 
  *  and if TRUE, initialize the vmcore_data structure.
  */
@@ -618,7 +656,7 @@ get_netdump_panic_task(void)
 		crashing_cpu = -1;
 		if (kernel_symbol_exists("crashing_cpu")) {
 			get_symbol_data("crashing_cpu", sizeof(int), &i);
-			if ((i >= 0) && (i < nd->num_prstatus_notes)) {
+			if ((i >= 0) && in_cpu_map(ONLINE, i)) {
 				crashing_cpu = i;
 				if (CRASHDEBUG(1))
 					error(INFO, 
@@ -2236,7 +2274,7 @@ get_netdump_regs_ppc64(struct bt_info *b
 		 * CPUs if they responded to an IPI.
 		 */
                 if (nd->num_prstatus_notes > 1) {
-			if (bt->tc->processor >= nd->num_prstatus_notes)
+			if (!nd->nt_prstatus_percpu[bt->tc->processor])
 				error(FATAL, 
 		          	    "cannot determine NT_PRSTATUS ELF note "
 				    "for %s task: %lx\n",