Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751883AbdFHCQr (ORCPT ); Wed, 7 Jun 2017 22:16:47 -0400 Received: from mail-ua0-f179.google.com ([209.85.217.179]:35839 "EHLO mail-ua0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751428AbdFHCQq (ORCPT ); Wed, 7 Jun 2017 22:16:46 -0400 MIME-Version: 1.0 In-Reply-To: <20170607143659.29013dd3@gandalf.local.home> References: <1496823171-7758-1-git-send-email-zhang.chunyan@linaro.org> <20170607143659.29013dd3@gandalf.local.home> From: Chunyan Zhang Date: Thu, 8 Jun 2017 10:16:44 +0800 Message-ID: Subject: Re: [RESEND PATCH v2] trace: fix the errors caused by incompatible type of RCU variables To: Steven Rostedt Cc: Ingo Molnar , "linux-kernel@vger.kernel.org" , Lyra Zhang Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8931 Lines: 222 On 8 June 2017 at 02:36, Steven Rostedt wrote: > On Wed, 7 Jun 2017 16:12:51 +0800 > Chunyan Zhang wrote: > >> The variables which are processed by RCU functions should be annotated >> as RCU, otherwise sparse will report the errors like below: >> >> "error: incompatible types in comparison expression (different >> address spaces)" >> >> Signed-off-by: Chunyan Zhang > > Hi, Hi Steve, > >> --- >> >> Changes in v2: >> * Addressed Steven's comments >> - Use rcu_dereference_protected() instead of rcu_dereference_raw_notrace() >> * Rebased on v4.12-rc1 >> >> include/linux/ftrace.h | 6 +++--- >> include/linux/trace_events.h | 2 +- >> kernel/trace/ftrace.c | 42 ++++++++++++++++++++++++++++-------------- >> kernel/trace/trace.h | 6 +++--- >> 4 files changed, 35 insertions(+), 21 deletions(-) >> >> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h >> index 473f088..056395c7 100644 >> --- a/include/linux/ftrace.h >> +++ b/include/linux/ftrace.h >> @@ -142,8 +142,8 @@ enum { >> #ifdef CONFIG_DYNAMIC_FTRACE >> /* The hash used to know what functions callbacks trace */ >> struct ftrace_ops_hash { >> - struct ftrace_hash *notrace_hash; >> - struct ftrace_hash *filter_hash; >> + struct ftrace_hash __rcu *notrace_hash; >> + struct ftrace_hash __rcu *filter_hash; >> struct mutex regex_lock; >> }; >> >> @@ -165,7 +165,7 @@ static inline void ftrace_free_init_mem(void) { } >> */ >> struct ftrace_ops { >> ftrace_func_t func; >> - struct ftrace_ops *next; >> + struct ftrace_ops __rcu *next; >> unsigned long flags; >> void *private; >> ftrace_func_t saved_func; >> diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h >> index a556805..89f7bd5d 100644 >> --- a/include/linux/trace_events.h >> +++ b/include/linux/trace_events.h >> @@ -327,7 +327,7 @@ enum { >> struct trace_event_file { >> struct list_head list; >> struct trace_event_call *event_call; >> - struct event_filter *filter; >> + struct event_filter __rcu *filter; >> struct dentry *dir; >> struct trace_array *tr; >> struct trace_subsystem_dir *system; >> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c >> index 39dca4e..116742b 100644 >> --- a/kernel/trace/ftrace.c >> +++ b/kernel/trace/ftrace.c >> @@ -113,7 +113,8 @@ static int ftrace_disabled __read_mostly; >> >> static DEFINE_MUTEX(ftrace_lock); >> >> -static struct ftrace_ops *ftrace_ops_list __read_mostly = &ftrace_list_end; >> +static struct ftrace_ops __rcu * >> + ftrace_ops_list __read_mostly = &ftrace_list_end; > > I may fix this myself, but newlines like the above is IMHO uglier than Good, thanks. > going over 80 characters. I much rather keep it on one line. > >> ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub; >> static struct ftrace_ops global_ops; >> >> @@ -169,8 +170,11 @@ int ftrace_nr_registered_ops(void) >> >> mutex_lock(&ftrace_lock); >> >> - for (ops = ftrace_ops_list; >> - ops != &ftrace_list_end; ops = ops->next) >> + for (ops = rcu_dereference_protected(ftrace_ops_list, >> + lockdep_is_held(&ftrace_lock)); >> + ops != &ftrace_list_end; >> + ops = rcu_dereference_protected(ops->next, >> + lockdep_is_held(&ftrace_lock))) >> cnt++; >> >> mutex_unlock(&ftrace_lock); >> @@ -275,10 +279,11 @@ static void update_ftrace_function(void) >> * If there's only one ftrace_ops registered, the ftrace_ops_list >> * will point to the ops we want. >> */ >> - set_function_trace_op = ftrace_ops_list; >> + set_function_trace_op = rcu_dereference_protected(ftrace_ops_list, >> + lockdep_is_held(&ftrace_lock)); >> >> /* If there's no ftrace_ops registered, just call the stub function */ >> - if (ftrace_ops_list == &ftrace_list_end) { >> + if (set_function_trace_op == &ftrace_list_end) { > > Slight change of code, but shouldn't have any affect on the flow. > >> func = ftrace_stub; >> >> /* >> @@ -286,7 +291,8 @@ static void update_ftrace_function(void) >> * recursion safe and not dynamic and the arch supports passing ops, >> * then have the mcount trampoline call the function directly. >> */ >> - } else if (ftrace_ops_list->next == &ftrace_list_end) { >> + } else if (rcu_dereference_protected(ftrace_ops_list->next, >> + lockdep_is_held(&ftrace_lock)) == &ftrace_list_end) { >> func = ftrace_ops_get_list_func(ftrace_ops_list); >> >> } else { >> @@ -348,9 +354,11 @@ int using_ftrace_ops_list_func(void) >> return ftrace_trace_function == ftrace_ops_list_func; >> } >> >> -static void add_ftrace_ops(struct ftrace_ops **list, struct ftrace_ops *ops) >> +static void add_ftrace_ops(struct ftrace_ops __rcu **list, >> + struct ftrace_ops *ops) >> { >> - ops->next = *list; >> + rcu_assign_pointer(ops->next, *list); >> + >> /* >> * We are entering ops into the list but another >> * CPU might be walking that list. We need to make sure >> @@ -360,7 +368,8 @@ static void add_ftrace_ops(struct ftrace_ops **list, struct ftrace_ops *ops) >> rcu_assign_pointer(*list, ops); >> } >> >> -static int remove_ftrace_ops(struct ftrace_ops **list, struct ftrace_ops *ops) >> +static int remove_ftrace_ops(struct ftrace_ops __rcu **list, >> + struct ftrace_ops *ops) >> { >> struct ftrace_ops **p; >> >> @@ -368,7 +377,10 @@ static int remove_ftrace_ops(struct ftrace_ops **list, struct ftrace_ops *ops) >> * If we are removing the last function, then simply point >> * to the ftrace_stub. >> */ >> - if (*list == ops && ops->next == &ftrace_list_end) { >> + if (rcu_dereference_protected(*list, >> + lockdep_is_held(&ftrace_lock)) == ops && >> + rcu_dereference_protected(ops->next, >> + lockdep_is_held(&ftrace_lock)) == &ftrace_list_end) { >> *list = &ftrace_list_end; >> return 0; >> } >> @@ -1513,8 +1525,8 @@ ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip, void *regs) >> return 0; >> #endif >> >> - hash.filter_hash = rcu_dereference_raw_notrace(ops->func_hash->filter_hash); >> - hash.notrace_hash = rcu_dereference_raw_notrace(ops->func_hash->notrace_hash); >> + rcu_assign_pointer(hash.filter_hash, ops->func_hash->filter_hash); >> + rcu_assign_pointer(hash.notrace_hash, ops->func_hash->notrace_hash); >> >> if (hash_contains_ip(ip, &hash)) >> ret = 1; >> @@ -2784,7 +2796,8 @@ static int ftrace_shutdown(struct ftrace_ops *ops, int command) >> * If there's no more ops registered with ftrace, run a >> * sanity check to make sure all rec flags are cleared. >> */ >> - if (ftrace_ops_list == &ftrace_list_end) { >> + if (rcu_dereference_protected(ftrace_ops_list, >> + lockdep_is_held(&ftrace_lock)) == &ftrace_list_end) { >> struct ftrace_page *pg; >> struct dyn_ftrace *rec; >> >> @@ -6122,7 +6135,8 @@ ftrace_enable_sysctl(struct ctl_table *table, int write, >> if (ftrace_enabled) { >> >> /* we are starting ftrace again */ >> - if (ftrace_ops_list != &ftrace_list_end) >> + if (rcu_dereference_protected(ftrace_ops_list, >> + lockdep_is_held(&ftrace_lock)) != &ftrace_list_end) >> update_ftrace_function(); >> >> ftrace_startup_sysctl(); >> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h >> index 291a1bc..60b26b4 100644 >> --- a/kernel/trace/trace.h >> +++ b/kernel/trace/trace.h >> @@ -1183,9 +1183,9 @@ struct ftrace_event_field { >> struct event_filter { >> int n_preds; /* Number assigned */ >> int a_preds; /* allocated */ >> - struct filter_pred *preds; >> - struct filter_pred *root; >> - char *filter_string; >> + struct filter_pred __rcu *preds; >> + struct filter_pred __rcu *root; >> + char *filter_string; >> }; >> >> struct event_subsystem { > > So far looks fine. I'll run it through my tests and see if it triggers > any lockdep issues. Thank you for the review and test, Chunyan > > -- Steve