On Thu, 2007-10-11 at 15:06 +0200, Jan Kiszka wrote:
> for_each_online_cpu is not free of function calls on SMP, thus causes
> false NMI noise in the tracer log (due to tracer recursions). Switch to
> some plain loop instead.
This one breaks badly on SMP, where NR_CPUS is likely greater than the
highest numbered CPU from the possible CPU map (at least if you don't
lower the former value at config time), so in the TRACE_VMALLOC case,
you end up dereferencing NULL trace_paths[] pointers.
Since we may not want to mark __next_cpu() and find_next_bit() as
notrace routines, we have to check the boundaries:
diff --git a/kernel/ipipe/tracer.c b/kernel/ipipe/tracer.c
index 2326706..8ecbe1a 100644
--- a/kernel/ipipe/tracer.c
+++ b/kernel/ipipe/tracer.c
@@ -255,7 +255,7 @@ __ipipe_trace_freeze(int cpu_id, struct ipipe_trace_path
*tp, int pos)
active = __ipipe_get_free_trace_path(active, cpu_id);
/* check if this is the first frozen path */
- for (i = 0; i < NR_CPUS; i++) {
+ for (i = 0; i < NR_CPUS && trace_paths[i] != NULL; i++) {
if ((i != cpu_id) &&
(trace_paths[i][frozen_path[i]].end >= 0))
tp->end = -1;
@@ -520,7 +520,7 @@ int ipipe_trace_max_reset(void)
flags = __ipipe_global_path_lock();
- for (cpu_id = 0; cpu_id < NR_CPUS; cpu_id++) {
+ for (cpu_id = 0; cpu_id < NR_CPUS && trace_paths[cpu_id] != NULL;
cpu_id++) {
path = &trace_paths[cpu_id][max_path[cpu_id]];
if (path->dump_lock) {
--
Philippe.
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