Messages in this thread Patch in this message | | | Date | Thu, 23 Jan 2020 13:10:10 +0100 | From | Jessica Yu <> | Subject | Re: [PATCH] kernel: module: Pass lockdep expression to RCU lists |
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+++ Amol Grover [21/01/20 18:17 +0530]: >modules is traversed using list_for_each_entry_rcu outside an >RCU read-side critical section but under the protection >of module_mutex or with preemption disabled. > >Hence, add corresponding lockdep expression to silence false-positive >lockdep warnings, and harden RCU lists. > >list_for_each_entry_rcu when traversed inside a preempt disabled >section, doesn't need an explicit lockdep expression since it is >implicitly checked for. > >Add macro for the corresponding lockdep expression. > >Signed-off-by: Amol Grover <frextrite@gmail.com>
Hi Amol!
Masami already submitted a patch for this, it's been in linux-next for a while. See commit bf08949cc8b9 ("modules: lockdep: Suppress suspicious RCU usage warning").
Thanks!
Jessica
>--- > kernel/module.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > >diff --git a/kernel/module.c b/kernel/module.c >index b56f3224b161..2425f58159dd 100644 >--- a/kernel/module.c >+++ b/kernel/module.c >@@ -84,6 +84,8 @@ > * 3) module_addr_min/module_addr_max. > * (delete and add uses RCU list operations). */ > DEFINE_MUTEX(module_mutex); >+#define module_mutex_held() \ >+ lockdep_is_held(&module_mutex) > EXPORT_SYMBOL_GPL(module_mutex); > static LIST_HEAD(modules); > >@@ -214,7 +216,7 @@ static struct module *mod_find(unsigned long addr) > { > struct module *mod; > >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, module_mutex_held()) { > if (within_module(addr, mod)) > return mod; > } >@@ -448,7 +450,7 @@ bool each_symbol_section(bool (*fn)(const struct symsearch *arr, > if (each_symbol_in_section(arr, ARRAY_SIZE(arr), NULL, fn, data)) > return true; > >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, module_mutex_held()) { > struct symsearch arr[] = { > { mod->syms, mod->syms + mod->num_syms, mod->crcs, > NOT_GPL_ONLY, false }, >@@ -616,7 +618,7 @@ static struct module *find_module_all(const char *name, size_t len, > > module_assert_mutex_or_preempt(); > >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, module_mutex_held()) { > if (!even_unformed && mod->state == MODULE_STATE_UNFORMED) > continue; > if (strlen(mod->name) == len && !memcmp(mod->name, name, len)) >@@ -2040,7 +2042,7 @@ void set_all_modules_text_rw(void) > return; > > mutex_lock(&module_mutex); >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, module_mutex_held()) { > if (mod->state == MODULE_STATE_UNFORMED) > continue; > >@@ -2059,7 +2061,7 @@ void set_all_modules_text_ro(void) > return; > > mutex_lock(&module_mutex); >- list_for_each_entry_rcu(mod, &modules, list) { >+ list_for_each_entry_rcu(mod, &modules, list, module_mutex_held()) { > /* > * Ignore going modules since it's possible that ro > * protection has already been disabled, otherwise we'll >-- >2.24.1 >
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