When traversing all nodes and moving to a new path component, the old one must be released by calling of_node_put(). Else the refcounts of the parent node(s) will not be decremented.
Signed-off-by: Geert Uytterhoeven <[email protected]> --- Background. While investigating a reference count imbalance issue with CONFIG_OF_DYNAMIC=y, I wrote the debug code below to validate the reference counts of the nodes I was interested in. During the first call of check_refcnts(), it gathers all reference counts. During a subsequent call, it verifies that they are still the same. Surprisingly, lots of reference counts were wrong, and kept incrementing every time check_refcnts() was called. I was just wondering whether it would be useful to have a reference count test in OF_UNITTEST, but now I see the "select OF_DYNAMIC" will go away? Feel free to (ab)use the code below and derive a unittest from it... static struct to_check { const char *path; int refcnt; } to_check[] = { { "/" }, { "/cpus/cpu@0" }, { "/cpus/cpu@1" }, /* ... other paths I was interested in ... */ }; static void check_refcnts(void) { static bool called; unsigned int i; const char *path; struct device_node *np; int refcnt; unsigned int errors = 0; pr_info("----- %s reference counts -----\n", called ? "Checking" : "Saving"); for (i = 0; i < ARRAY_SIZE(to_check); i++) { path = to_check[i].path; np = of_find_node_by_path(path); if (!np) continue; refcnt = atomic_read(&np->kobj.kref.refcount); if (!called) { pr_info("%s %d\n", path, refcnt); to_check[i].refcnt = refcnt; } else if (refcnt == to_check[i].refcnt) { pr_info("%s %d (OK)\n", path, refcnt); } else { pr_info("%s %d (should be %d)\n", path, refcnt, to_check[i].refcnt); errors++; } of_node_put(np); } if (called) pr_info("----- Checking done (%u errors) -----\n", errors); else pr_info("----- Saving done -----\n"); called = true; } --- drivers/of/base.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/of/base.c b/drivers/of/base.c index 36536b6a8834acd2..f3e346e19c69d1f2 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c @@ -791,8 +791,10 @@ struct device_node *of_find_node_opts_by_path(const char *path, const char **opt if (!np) np = of_node_get(of_root); while (np && *path == '/') { + struct device_node *parent = np; path++; /* Increment past '/' delimiter */ - np = __of_find_node_by_path(np, path); + np = __of_find_node_by_path(parent, path); + of_node_put(parent); path = strchrnul(path, '/'); } raw_spin_unlock_irqrestore(&devtree_lock, flags); -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
