On 9/26/22 23:47, David Matlack wrote:
How about this?
diff --git a/tools/testing/selftests/kvm/lib/assert.c b/tools/testing/selftests/kvm/lib/assert.c
index 71ade6100fd3..2b56bbff970c 100644
--- a/tools/testing/selftests/kvm/lib/assert.c
+++ b/tools/testing/selftests/kvm/lib/assert.c
@@ -38,16 +38,28 @@ static void test_dump_stack(void)
1];
char *c;
- n = backtrace(stack, n);
c = &cmd[0];
c += sprintf(c, "%s", addr2line);
- /*
- * Skip the first 3 frames: backtrace, test_dump_stack, and
- * test_assert. We hope that backtrace isn't inlined and the other two
- * we've declared noinline.
- */
- for (i = 2; i < n; i++)
- c += sprintf(c, " %lx", ((unsigned long) stack[i]) - 1);
+
+ n = backtrace(stack, n);
+ if (n > 2) {
+ /*
+ * Skip the first 2 frames, which should be test_dump_stack()
+ * and test_assert(); both of which are declared noinline.
+ */
+ for (i = 2; i < n; i++)
+ c += sprintf(c, " %lx", ((unsigned long) stack[i]) - 1);
+ } else {
+ /*
+ * Bail if the resulting stack trace would be empty. Otherwise,
+ * addr2line will block waiting for addresses to be passed in
+ * via stdin.
+ */
+ fputs(" (stack trace missing)\n", stderr);
+ return;
+ }
+
c += sprintf(c, "%s", pipeline);
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-result"
I think your original patch is better, just with
diff --git a/tools/testing/selftests/kvm/lib/assert.c b/tools/testing/selftests/kvm/lib/assert.c
index c1ce54a41eca..be2cab00f541 100644
--- a/tools/testing/selftests/kvm/lib/assert.c
+++ b/tools/testing/selftests/kvm/lib/assert.c
@@ -36,11 +36,9 @@ static void test_dump_stack(void)
n * (((sizeof(void *)) * 2) + 1) +
/* Null terminator: */
1];
- char *c;
+ char *c = cmd;
n = backtrace(stack, n);
- c = &cmd[0];
- c += sprintf(c, "%s", addr2line);
/*
* Skip the first 2 frames, which should be test_dump_stack() and
* test_assert(); both of which are declared noinline. Bail if the
@@ -51,6 +49,8 @@ static void test_dump_stack(void)
fputs(" (stack trace empty)\n", stderr);
return;
}
+
+ c += sprintf(c, "%s", addr2line);
for (i = 2; i < n; i++)
c += sprintf(c, " %lx", ((unsigned long) stack[i]) - 1);
squashed in to keep the "if" and backtrace() call as close as possible.
Paolo
