| Message ID | 1476778140-10319-2-git-send-email-zhang.chunyan@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
On Tue, 18 Oct 2016 16:08:58 +0800 Chunyan Zhang <zhang.chunyan@linaro.org> wrote: > Currently Function traces can be only exported to ring buffer, this > patch added trace_export concept which can process traces and export > them to a registered destination as an addition to the current only > one output of Ftrace - i.e. ring buffer. > > In this way, if we want Function traces to be sent to other destination > rather than ring buffer only, we just need to register a new trace_export > and implement its own .write() function for writing traces to storage. > > With this patch, only Function trace (trace type is TRACE_FN) > is supported. This is getting better, but I still have some nits. > > Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org> > --- > include/linux/trace.h | 28 +++++++++++ > kernel/trace/trace.c | 132 +++++++++++++++++++++++++++++++++++++++++++++++++- > 2 files changed, 159 insertions(+), 1 deletion(-) > create mode 100644 include/linux/trace.h > > diff --git a/include/linux/trace.h b/include/linux/trace.h > new file mode 100644 > index 0000000..eb1c5b8 > --- /dev/null > +++ b/include/linux/trace.h > @@ -0,0 +1,28 @@ > +#ifndef _LINUX_TRACE_H > +#define _LINUX_TRACE_H > + > +#ifdef CONFIG_TRACING > +/* > + * The trace export - an export of Ftrace output. The trace_export > + * can process traces and export them to a registered destination as > + * an addition to the current only output of Ftrace - i.e. ring buffer. > + * > + * If you want traces to be sent to some other place rather than ring > + * buffer only, just need to register a new trace_export and implement > + * its own .write() function for writing traces to the storage. > + * > + * next - pointer to the next trace_export > + * write - copy traces which have been delt with ->commit() to > + * the destination > + */ > +struct trace_export { > + struct trace_export __rcu *next; > + void (*write)(const char *, unsigned int); Why const char*? Why not const void *? This will never be a string. > +}; > + > +int register_ftrace_export(struct trace_export *export); > +int unregister_ftrace_export(struct trace_export *export); > + > +#endif /* CONFIG_TRACING */ > + > +#endif /* _LINUX_TRACE_H */ > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 8696ce6..db94ec1 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -40,6 +40,7 @@ > #include <linux/poll.h> > #include <linux/nmi.h> > #include <linux/fs.h> > +#include <linux/trace.h> > #include <linux/sched/rt.h> > > #include "trace.h" > @@ -2128,6 +2129,132 @@ void trace_buffer_unlock_commit_regs(struct trace_array *tr, > ftrace_trace_userstack(buffer, flags, pc); > } > > +static void > +trace_process_export(struct trace_export *export, > + struct ring_buffer_event *event) > +{ > + struct trace_entry *entry; > + unsigned int size = 0; > + > + entry = ring_buffer_event_data(event); > + > + size = ring_buffer_event_length(event); > + > + if (export->write) > + export->write((char *)entry, size); Is there ever going to be a time where export->write wont be set? And if there is, this can be racy. As in CPU 0: CPU 1: ------ ------ if (export->write) export->write = NULL; export->write(entry, size); BOOM! -- Steve > +} > + > +static DEFINE_MUTEX(ftrace_export_lock); > + > +static struct trace_export __rcu *ftrace_exports_list __read_mostly; > + > +static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled); > + > +static inline void ftrace_exports_enable(void) > +{ > + static_branch_enable(&ftrace_exports_enabled); > +} > + > +static inline void ftrace_exports_disable(void) > +{ > + static_branch_disable(&ftrace_exports_enabled); > +} > + > +void ftrace_exports(struct ring_buffer_event *event) > +{ > + struct trace_export *export; > + > + preempt_disable_notrace(); > + > + export = rcu_dereference_raw_notrace(ftrace_exports_list); > + while (export) { > + trace_process_export(export, event); > + export = rcu_dereference_raw_notrace(export->next); > + } > + > + preempt_enable_notrace(); > +} > + > +static inline void > +add_trace_export(struct trace_export **list, struct trace_export *export) > +{ > + rcu_assign_pointer(export->next, *list); > + /* > + * We are entering export into the list but another > + * CPU might be walking that list. We need to make sure > + * the export->next pointer is valid before another CPU sees > + * the export pointer included into the list. > + */ > + rcu_assign_pointer(*list, export); > +} > + > +static inline int > +rm_trace_export(struct trace_export **list, struct trace_export *export) > +{ > + struct trace_export **p; > + > + for (p = list; *p != NULL; p = &(*p)->next) > + if (*p == export) > + break; > + > + if (*p != export) > + return -1; > + > + rcu_assign_pointer(*p, (*p)->next); > + > + return 0; > +} > + > +static inline void > +add_ftrace_export(struct trace_export **list, struct trace_export *export) > +{ > + if (*list == NULL) > + ftrace_exports_enable(); > + > + add_trace_export(list, export); > +} > + > +static inline int > +rm_ftrace_export(struct trace_export **list, struct trace_export *export) > +{ > + int ret; > + > + ret = rm_trace_export(list, export); > + if (*list == NULL) > + ftrace_exports_disable(); > + > + return ret; > +} > + > +int register_ftrace_export(struct trace_export *export) > +{ > + if (WARN_ON_ONCE(!export->write)) > + return -1; > + > + mutex_lock(&ftrace_export_lock); > + > + add_ftrace_export(&ftrace_exports_list, export); > + > + mutex_unlock(&ftrace_export_lock); > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(register_ftrace_export); > + > +int unregister_ftrace_export(struct trace_export *export) > +{ > + int ret; > + > + mutex_lock(&ftrace_export_lock); > + > + ret = rm_ftrace_export(&ftrace_exports_list, export); > + > + mutex_unlock(&ftrace_export_lock); > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(unregister_ftrace_export); > + > void > trace_function(struct trace_array *tr, > unsigned long ip, unsigned long parent_ip, unsigned long flags, > @@ -2146,8 +2273,11 @@ trace_function(struct trace_array *tr, > entry->ip = ip; > entry->parent_ip = parent_ip; > > - if (!call_filter_check_discard(call, entry, buffer, event)) > + if (!call_filter_check_discard(call, entry, buffer, event)) { > + if (static_branch_unlikely(&ftrace_exports_enabled)) > + ftrace_exports(event); > __buffer_unlock_commit(buffer, event); > + } > } > > #ifdef CONFIG_STACKTRACE
On 18 October 2016 at 23:44, Steven Rostedt <rostedt@goodmis.org> wrote: > On Tue, 18 Oct 2016 16:08:58 +0800 > Chunyan Zhang <zhang.chunyan@linaro.org> wrote: > >> Currently Function traces can be only exported to ring buffer, this >> patch added trace_export concept which can process traces and export >> them to a registered destination as an addition to the current only >> one output of Ftrace - i.e. ring buffer. >> >> In this way, if we want Function traces to be sent to other destination >> rather than ring buffer only, we just need to register a new trace_export >> and implement its own .write() function for writing traces to storage. >> >> With this patch, only Function trace (trace type is TRACE_FN) >> is supported. > > This is getting better, but I still have some nits. > Thanks. >> >> Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org> >> --- >> include/linux/trace.h | 28 +++++++++++ >> kernel/trace/trace.c | 132 +++++++++++++++++++++++++++++++++++++++++++++++++- >> 2 files changed, 159 insertions(+), 1 deletion(-) >> create mode 100644 include/linux/trace.h >> >> diff --git a/include/linux/trace.h b/include/linux/trace.h >> new file mode 100644 >> index 0000000..eb1c5b8 >> --- /dev/null >> +++ b/include/linux/trace.h >> @@ -0,0 +1,28 @@ >> +#ifndef _LINUX_TRACE_H >> +#define _LINUX_TRACE_H >> + >> +#ifdef CONFIG_TRACING >> +/* >> + * The trace export - an export of Ftrace output. The trace_export >> + * can process traces and export them to a registered destination as >> + * an addition to the current only output of Ftrace - i.e. ring buffer. >> + * >> + * If you want traces to be sent to some other place rather than ring >> + * buffer only, just need to register a new trace_export and implement >> + * its own .write() function for writing traces to the storage. >> + * >> + * next - pointer to the next trace_export >> + * write - copy traces which have been delt with ->commit() to >> + * the destination >> + */ >> +struct trace_export { >> + struct trace_export __rcu *next; >> + void (*write)(const char *, unsigned int); > > Why const char*? Why not const void *? This will never be a string. > Will revise this. > >> +}; >> + >> +int register_ftrace_export(struct trace_export *export); >> +int unregister_ftrace_export(struct trace_export *export); >> + >> +#endif /* CONFIG_TRACING */ >> + >> +#endif /* _LINUX_TRACE_H */ >> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c >> index 8696ce6..db94ec1 100644 >> --- a/kernel/trace/trace.c >> +++ b/kernel/trace/trace.c >> @@ -40,6 +40,7 @@ >> #include <linux/poll.h> >> #include <linux/nmi.h> >> #include <linux/fs.h> >> +#include <linux/trace.h> >> #include <linux/sched/rt.h> >> >> #include "trace.h" >> @@ -2128,6 +2129,132 @@ void trace_buffer_unlock_commit_regs(struct trace_array *tr, >> ftrace_trace_userstack(buffer, flags, pc); >> } >> >> +static void >> +trace_process_export(struct trace_export *export, >> + struct ring_buffer_event *event) >> +{ >> + struct trace_entry *entry; >> + unsigned int size = 0; >> + >> + entry = ring_buffer_event_data(event); >> + >> + size = ring_buffer_event_length(event); >> + >> + if (export->write) >> + export->write((char *)entry, size); > > Is there ever going to be a time where export->write wont be set? There hasn't been since only one trace_export (i.e. stm_ftrace) was added in this patch-set , I just wanted to make sure the write() has been set before registering trace_export like what I added in 2/3 of this series. > > And if there is, this can be racy. As in > > > CPU 0: CPU 1: > ------ ------ > if (export->write) > > export->write = NULL; Is there going to be this kind of use case? Why some one needs to change export->write() rather than register a new trace_export? I probably haven't understood your point thoroughly, please correct me if my guess was wrong. Thanks for the review, Chunyan > > export->write(entry, size); > > BOOM! > > > -- Steve > >> +} >> + >> +static DEFINE_MUTEX(ftrace_export_lock); >> + >> +static struct trace_export __rcu *ftrace_exports_list __read_mostly; >> + >> +static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled); >> + >> +static inline void ftrace_exports_enable(void) >> +{ >> + static_branch_enable(&ftrace_exports_enabled); >> +} >> + >> +static inline void ftrace_exports_disable(void) >> +{ >> + static_branch_disable(&ftrace_exports_enabled); >> +} >> + >> +void ftrace_exports(struct ring_buffer_event *event) >> +{ >> + struct trace_export *export; >> + >> + preempt_disable_notrace(); >> + >> + export = rcu_dereference_raw_notrace(ftrace_exports_list); >> + while (export) { >> + trace_process_export(export, event); >> + export = rcu_dereference_raw_notrace(export->next); >> + } >> + >> + preempt_enable_notrace(); >> +} >> + >> +static inline void >> +add_trace_export(struct trace_export **list, struct trace_export *export) >> +{ >> + rcu_assign_pointer(export->next, *list); >> + /* >> + * We are entering export into the list but another >> + * CPU might be walking that list. We need to make sure >> + * the export->next pointer is valid before another CPU sees >> + * the export pointer included into the list. >> + */ >> + rcu_assign_pointer(*list, export); >> +} >> + >> +static inline int >> +rm_trace_export(struct trace_export **list, struct trace_export *export) >> +{ >> + struct trace_export **p; >> + >> + for (p = list; *p != NULL; p = &(*p)->next) >> + if (*p == export) >> + break; >> + >> + if (*p != export) >> + return -1; >> + >> + rcu_assign_pointer(*p, (*p)->next); >> + >> + return 0; >> +} >> + >> +static inline void >> +add_ftrace_export(struct trace_export **list, struct trace_export *export) >> +{ >> + if (*list == NULL) >> + ftrace_exports_enable(); >> + >> + add_trace_export(list, export); >> +} >> + >> +static inline int >> +rm_ftrace_export(struct trace_export **list, struct trace_export *export) >> +{ >> + int ret; >> + >> + ret = rm_trace_export(list, export); >> + if (*list == NULL) >> + ftrace_exports_disable(); >> + >> + return ret; >> +} >> + >> +int register_ftrace_export(struct trace_export *export) >> +{ >> + if (WARN_ON_ONCE(!export->write)) >> + return -1; >> + >> + mutex_lock(&ftrace_export_lock); >> + >> + add_ftrace_export(&ftrace_exports_list, export); >> + >> + mutex_unlock(&ftrace_export_lock); >> + >> + return 0; >> +} >> +EXPORT_SYMBOL_GPL(register_ftrace_export); >> + >> +int unregister_ftrace_export(struct trace_export *export) >> +{ >> + int ret; >> + >> + mutex_lock(&ftrace_export_lock); >> + >> + ret = rm_ftrace_export(&ftrace_exports_list, export); >> + >> + mutex_unlock(&ftrace_export_lock); >> + >> + return ret; >> +} >> +EXPORT_SYMBOL_GPL(unregister_ftrace_export); >> + >> void >> trace_function(struct trace_array *tr, >> unsigned long ip, unsigned long parent_ip, unsigned long flags, >> @@ -2146,8 +2273,11 @@ trace_function(struct trace_array *tr, >> entry->ip = ip; >> entry->parent_ip = parent_ip; >> >> - if (!call_filter_check_discard(call, entry, buffer, event)) >> + if (!call_filter_check_discard(call, entry, buffer, event)) { >> + if (static_branch_unlikely(&ftrace_exports_enabled)) >> + ftrace_exports(event); >> __buffer_unlock_commit(buffer, event); >> + } >> } >> >> #ifdef CONFIG_STACKTRACE >
Hi Steve, Resend this since the subject was lost in the prior one due to unknown reason. On 21 October 2016 at 20:13, Chunyan Zhang <zhang.chunyan@linaro.org> wrote: > On 18 October 2016 at 23:44, Steven Rostedt <rostedt@goodmis.org> wrote: >> On Tue, 18 Oct 2016 16:08:58 +0800 >> Chunyan Zhang <zhang.chunyan@linaro.org> wrote: >> >>> Currently Function traces can be only exported to ring buffer, this >>> patch added trace_export concept which can process traces and export >>> them to a registered destination as an addition to the current only >>> one output of Ftrace - i.e. ring buffer. >>> >>> In this way, if we want Function traces to be sent to other destination >>> rather than ring buffer only, we just need to register a new trace_export >>> and implement its own .write() function for writing traces to storage. >>> >>> With this patch, only Function trace (trace type is TRACE_FN) >>> is supported. >> >> This is getting better, but I still have some nits. >> > > Thanks. > >>> >>> Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org> >>> --- >>> include/linux/trace.h | 28 +++++++++++ >>> kernel/trace/trace.c | 132 +++++++++++++++++++++++++++++++++++++++++++++++++- >>> 2 files changed, 159 insertions(+), 1 deletion(-) >>> create mode 100644 include/linux/trace.h >>> >>> diff --git a/include/linux/trace.h b/include/linux/trace.h >>> new file mode 100644 >>> index 0000000..eb1c5b8 >>> --- /dev/null >>> +++ b/include/linux/trace.h >>> @@ -0,0 +1,28 @@ >>> +#ifndef _LINUX_TRACE_H >>> +#define _LINUX_TRACE_H >>> + >>> +#ifdef CONFIG_TRACING >>> +/* >>> + * The trace export - an export of Ftrace output. The trace_export >>> + * can process traces and export them to a registered destination as >>> + * an addition to the current only output of Ftrace - i.e. ring buffer. >>> + * >>> + * If you want traces to be sent to some other place rather than ring >>> + * buffer only, just need to register a new trace_export and implement >>> + * its own .write() function for writing traces to the storage. >>> + * >>> + * next - pointer to the next trace_export >>> + * write - copy traces which have been delt with ->commit() to >>> + * the destination >>> + */ >>> +struct trace_export { >>> + struct trace_export __rcu *next; >>> + void (*write)(const char *, unsigned int); >> >> Why const char*? Why not const void *? This will never be a string. >> > > Will revise this. > >> >>> +}; >>> + >>> +int register_ftrace_export(struct trace_export *export); >>> +int unregister_ftrace_export(struct trace_export *export); >>> + >>> +#endif /* CONFIG_TRACING */ >>> + >>> +#endif /* _LINUX_TRACE_H */ >>> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c >>> index 8696ce6..db94ec1 100644 >>> --- a/kernel/trace/trace.c >>> +++ b/kernel/trace/trace.c >>> @@ -40,6 +40,7 @@ >>> #include <linux/poll.h> >>> #include <linux/nmi.h> >>> #include <linux/fs.h> >>> +#include <linux/trace.h> >>> #include <linux/sched/rt.h> >>> >>> #include "trace.h" >>> @@ -2128,6 +2129,132 @@ void trace_buffer_unlock_commit_regs(struct trace_array *tr, >>> ftrace_trace_userstack(buffer, flags, pc); >>> } >>> >>> +static void >>> +trace_process_export(struct trace_export *export, >>> + struct ring_buffer_event *event) >>> +{ >>> + struct trace_entry *entry; >>> + unsigned int size = 0; >>> + >>> + entry = ring_buffer_event_data(event); >>> + >>> + size = ring_buffer_event_length(event); >>> + >>> + if (export->write) >>> + export->write((char *)entry, size); >> >> Is there ever going to be a time where export->write wont be set? > > There hasn't been since only one trace_export (i.e. stm_ftrace) was > added in this patch-set , I just wanted to make sure the write() has > been set before registering trace_export like what I added in 2/3 of > this series. > >> >> And if there is, this can be racy. As in >> >> >> CPU 0: CPU 1: >> ------ ------ >> if (export->write) >> >> export->write = NULL; > > Is there going to be this kind of use case? Why some one needs to > change export->write() rather than register a new trace_export? > > I probably haven't understood your point thoroughly, please correct me > if my guess was wrong. > Any further comments? :) Thanks, Chunyan > > Thanks for the review, > Chunyan > >> >> export->write(entry, size); >> >> BOOM! >> >> >> -- Steve >> >>> +} >>> + >>> +static DEFINE_MUTEX(ftrace_export_lock); >>> + >>> +static struct trace_export __rcu *ftrace_exports_list __read_mostly; >>> + >>> +static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled); >>> + >>> +static inline void ftrace_exports_enable(void) >>> +{ >>> + static_branch_enable(&ftrace_exports_enabled); >>> +} >>> + >>> +static inline void ftrace_exports_disable(void) >>> +{ >>> + static_branch_disable(&ftrace_exports_enabled); >>> +} >>> + >>> +void ftrace_exports(struct ring_buffer_event *event) >>> +{ >>> + struct trace_export *export; >>> + >>> + preempt_disable_notrace(); >>> + >>> + export = rcu_dereference_raw_notrace(ftrace_exports_list); >>> + while (export) { >>> + trace_process_export(export, event); >>> + export = rcu_dereference_raw_notrace(export->next); >>> + } >>> + >>> + preempt_enable_notrace(); >>> +} >>> + >>> +static inline void >>> +add_trace_export(struct trace_export **list, struct trace_export *export) >>> +{ >>> + rcu_assign_pointer(export->next, *list); >>> + /* >>> + * We are entering export into the list but another >>> + * CPU might be walking that list. We need to make sure >>> + * the export->next pointer is valid before another CPU sees >>> + * the export pointer included into the list. >>> + */ >>> + rcu_assign_pointer(*list, export); >>> +} >>> + >>> +static inline int >>> +rm_trace_export(struct trace_export **list, struct trace_export *export) >>> +{ >>> + struct trace_export **p; >>> + >>> + for (p = list; *p != NULL; p = &(*p)->next) >>> + if (*p == export) >>> + break; >>> + >>> + if (*p != export) >>> + return -1; >>> + >>> + rcu_assign_pointer(*p, (*p)->next); >>> + >>> + return 0; >>> +} >>> + >>> +static inline void >>> +add_ftrace_export(struct trace_export **list, struct trace_export *export) >>> +{ >>> + if (*list == NULL) >>> + ftrace_exports_enable(); >>> + >>> + add_trace_export(list, export); >>> +} >>> + >>> +static inline int >>> +rm_ftrace_export(struct trace_export **list, struct trace_export *export) >>> +{ >>> + int ret; >>> + >>> + ret = rm_trace_export(list, export); >>> + if (*list == NULL) >>> + ftrace_exports_disable(); >>> + >>> + return ret; >>> +} >>> + >>> +int register_ftrace_export(struct trace_export *export) >>> +{ >>> + if (WARN_ON_ONCE(!export->write)) >>> + return -1; >>> + >>> + mutex_lock(&ftrace_export_lock); >>> + >>> + add_ftrace_export(&ftrace_exports_list, export); >>> + >>> + mutex_unlock(&ftrace_export_lock); >>> + >>> + return 0; >>> +} >>> +EXPORT_SYMBOL_GPL(register_ftrace_export); >>> + >>> +int unregister_ftrace_export(struct trace_export *export) >>> +{ >>> + int ret; >>> + >>> + mutex_lock(&ftrace_export_lock); >>> + >>> + ret = rm_ftrace_export(&ftrace_exports_list, export); >>> + >>> + mutex_unlock(&ftrace_export_lock); >>> + >>> + return ret; >>> +} >>> +EXPORT_SYMBOL_GPL(unregister_ftrace_export); >>> + >>> void >>> trace_function(struct trace_array *tr, >>> unsigned long ip, unsigned long parent_ip, unsigned long flags, >>> @@ -2146,8 +2273,11 @@ trace_function(struct trace_array *tr, >>> entry->ip = ip; >>> entry->parent_ip = parent_ip; >>> >>> - if (!call_filter_check_discard(call, entry, buffer, event)) >>> + if (!call_filter_check_discard(call, entry, buffer, event)) { >>> + if (static_branch_unlikely(&ftrace_exports_enabled)) >>> + ftrace_exports(event); >>> __buffer_unlock_commit(buffer, event); >>> + } >>> } >>> >>> #ifdef CONFIG_STACKTRACE >>
On Fri, 21 Oct 2016 20:13:13 +0800 Chunyan Zhang <zhang.chunyan@linaro.org> wrote: > On 18 October 2016 at 23:44, Steven Rostedt <rostedt@goodmis.org> wrote: > > On Tue, 18 Oct 2016 16:08:58 +0800 > > Chunyan Zhang <zhang.chunyan@linaro.org> wrote: > > > >> Currently Function traces can be only exported to ring buffer, this > >> patch added trace_export concept which can process traces and export > >> them to a registered destination as an addition to the current only > >> one output of Ftrace - i.e. ring buffer. > >> > >> In this way, if we want Function traces to be sent to other destination > >> rather than ring buffer only, we just need to register a new trace_export > >> and implement its own .write() function for writing traces to storage. > >> > >> With this patch, only Function trace (trace type is TRACE_FN) > >> is supported. > > > > This is getting better, but I still have some nits. > > > > Thanks. > > >> > >> Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org> > >> --- > >> include/linux/trace.h | 28 +++++++++++ > >> kernel/trace/trace.c | 132 +++++++++++++++++++++++++++++++++++++++++++++++++- > >> 2 files changed, 159 insertions(+), 1 deletion(-) > >> create mode 100644 include/linux/trace.h > >> > >> diff --git a/include/linux/trace.h b/include/linux/trace.h > >> new file mode 100644 > >> index 0000000..eb1c5b8 > >> --- /dev/null > >> +++ b/include/linux/trace.h > >> @@ -0,0 +1,28 @@ > >> +#ifndef _LINUX_TRACE_H > >> +#define _LINUX_TRACE_H > >> + > >> +#ifdef CONFIG_TRACING > >> +/* > >> + * The trace export - an export of Ftrace output. The trace_export > >> + * can process traces and export them to a registered destination as > >> + * an addition to the current only output of Ftrace - i.e. ring buffer. > >> + * > >> + * If you want traces to be sent to some other place rather than ring > >> + * buffer only, just need to register a new trace_export and implement > >> + * its own .write() function for writing traces to the storage. > >> + * > >> + * next - pointer to the next trace_export > >> + * write - copy traces which have been delt with ->commit() to > >> + * the destination > >> + */ > >> +struct trace_export { > >> + struct trace_export __rcu *next; > >> + void (*write)(const char *, unsigned int); > > > > Why const char*? Why not const void *? This will never be a string. > > > > Will revise this. > > > > >> +}; > >> + > >> +int register_ftrace_export(struct trace_export *export); > >> +int unregister_ftrace_export(struct trace_export *export); > >> + > >> +#endif /* CONFIG_TRACING */ > >> + > >> +#endif /* _LINUX_TRACE_H */ > >> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > >> index 8696ce6..db94ec1 100644 > >> --- a/kernel/trace/trace.c > >> +++ b/kernel/trace/trace.c > >> @@ -40,6 +40,7 @@ > >> #include <linux/poll.h> > >> #include <linux/nmi.h> > >> #include <linux/fs.h> > >> +#include <linux/trace.h> > >> #include <linux/sched/rt.h> > >> > >> #include "trace.h" > >> @@ -2128,6 +2129,132 @@ void trace_buffer_unlock_commit_regs(struct trace_array *tr, > >> ftrace_trace_userstack(buffer, flags, pc); > >> } > >> > >> +static void > >> +trace_process_export(struct trace_export *export, > >> + struct ring_buffer_event *event) > >> +{ > >> + struct trace_entry *entry; > >> + unsigned int size = 0; > >> + > >> + entry = ring_buffer_event_data(event); > >> + > >> + size = ring_buffer_event_length(event); > >> + > >> + if (export->write) > >> + export->write((char *)entry, size); > > > > Is there ever going to be a time where export->write wont be set? > > There hasn't been since only one trace_export (i.e. stm_ftrace) was > added in this patch-set , I just wanted to make sure the write() has > been set before registering trace_export like what I added in 2/3 of > this series. > > > > > And if there is, this can be racy. As in > > > > > > CPU 0: CPU 1: > > ------ ------ > > if (export->write) > > > > export->write = NULL; > > Is there going to be this kind of use case? Why some one needs to > change export->write() rather than register a new trace_export? Then why have a if (export->write) Is there every going to be a case where export will not have a write function? -- Steve > > I probably haven't understood your point thoroughly, please correct me > if my guess was wrong. > > > Thanks for the review, > Chunyan > > > > > export->write(entry, size); > > > > BOOM! > > > > > > -- Steve
On 14 November 2016 at 23:59, Steven Rostedt <rostedt@goodmis.org> wrote: > On Fri, 21 Oct 2016 20:13:13 +0800 > Chunyan Zhang <zhang.chunyan@linaro.org> wrote: > >> On 18 October 2016 at 23:44, Steven Rostedt <rostedt@goodmis.org> wrote: >> > On Tue, 18 Oct 2016 16:08:58 +0800 >> > Chunyan Zhang <zhang.chunyan@linaro.org> wrote: >> > >> >> Currently Function traces can be only exported to ring buffer, this >> >> patch added trace_export concept which can process traces and export >> >> them to a registered destination as an addition to the current only >> >> one output of Ftrace - i.e. ring buffer. >> >> >> >> In this way, if we want Function traces to be sent to other destination >> >> rather than ring buffer only, we just need to register a new trace_export >> >> and implement its own .write() function for writing traces to storage. >> >> >> >> With this patch, only Function trace (trace type is TRACE_FN) >> >> is supported. >> > >> > This is getting better, but I still have some nits. >> > >> >> Thanks. >> >> >> >> >> Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org> >> >> --- >> >> include/linux/trace.h | 28 +++++++++++ >> >> kernel/trace/trace.c | 132 +++++++++++++++++++++++++++++++++++++++++++++++++- >> >> 2 files changed, 159 insertions(+), 1 deletion(-) >> >> create mode 100644 include/linux/trace.h >> >> >> >> diff --git a/include/linux/trace.h b/include/linux/trace.h >> >> new file mode 100644 >> >> index 0000000..eb1c5b8 >> >> --- /dev/null >> >> +++ b/include/linux/trace.h >> >> @@ -0,0 +1,28 @@ >> >> +#ifndef _LINUX_TRACE_H >> >> +#define _LINUX_TRACE_H >> >> + >> >> +#ifdef CONFIG_TRACING >> >> +/* >> >> + * The trace export - an export of Ftrace output. The trace_export >> >> + * can process traces and export them to a registered destination as >> >> + * an addition to the current only output of Ftrace - i.e. ring buffer. >> >> + * >> >> + * If you want traces to be sent to some other place rather than ring >> >> + * buffer only, just need to register a new trace_export and implement >> >> + * its own .write() function for writing traces to the storage. >> >> + * >> >> + * next - pointer to the next trace_export >> >> + * write - copy traces which have been delt with ->commit() to >> >> + * the destination >> >> + */ >> >> +struct trace_export { >> >> + struct trace_export __rcu *next; >> >> + void (*write)(const char *, unsigned int); >> > >> > Why const char*? Why not const void *? This will never be a string. >> > >> >> Will revise this. >> >> > >> >> +}; >> >> + >> >> +int register_ftrace_export(struct trace_export *export); >> >> +int unregister_ftrace_export(struct trace_export *export); >> >> + >> >> +#endif /* CONFIG_TRACING */ >> >> + >> >> +#endif /* _LINUX_TRACE_H */ >> >> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c >> >> index 8696ce6..db94ec1 100644 >> >> --- a/kernel/trace/trace.c >> >> +++ b/kernel/trace/trace.c >> >> @@ -40,6 +40,7 @@ >> >> #include <linux/poll.h> >> >> #include <linux/nmi.h> >> >> #include <linux/fs.h> >> >> +#include <linux/trace.h> >> >> #include <linux/sched/rt.h> >> >> >> >> #include "trace.h" >> >> @@ -2128,6 +2129,132 @@ void trace_buffer_unlock_commit_regs(struct trace_array *tr, >> >> ftrace_trace_userstack(buffer, flags, pc); >> >> } >> >> >> >> +static void >> >> +trace_process_export(struct trace_export *export, >> >> + struct ring_buffer_event *event) >> >> +{ >> >> + struct trace_entry *entry; >> >> + unsigned int size = 0; >> >> + >> >> + entry = ring_buffer_event_data(event); >> >> + >> >> + size = ring_buffer_event_length(event); >> >> + >> >> + if (export->write) >> >> + export->write((char *)entry, size); >> > >> > Is there ever going to be a time where export->write wont be set? >> >> There hasn't been since only one trace_export (i.e. stm_ftrace) was >> added in this patch-set , I just wanted to make sure the write() has >> been set before registering trace_export like what I added in 2/3 of >> this series. >> >> > >> > And if there is, this can be racy. As in >> > >> > >> > CPU 0: CPU 1: >> > ------ ------ >> > if (export->write) >> > >> > export->write = NULL; >> >> Is there going to be this kind of use case? Why some one needs to >> change export->write() rather than register a new trace_export? > > Then why have a > > if (export->write) > > > Is there every going to be a case where export will not have a write > function? There shouldn't be. I can move this if statement to the register_ftrace_export() to ensure users won't wrongly use it, that's saying the write() of trace_export has been set before being registered to 'ftrace_exports_list'. Thanks, Chunyan > > -- Steve > >> >> I probably haven't understood your point thoroughly, please correct me >> if my guess was wrong. >> >> >> Thanks for the review, >> Chunyan >> >> > >> > export->write(entry, size); >> > >> > BOOM! >> > >> > >> > -- Steve
On Tue, 15 Nov 2016 16:14:29 +0800 Chunyan Zhang <zhang.chunyan@linaro.org> wrote: > > > Then why have a > > > > if (export->write) > > > > > > Is there every going to be a case where export will not have a write > > function? > > There shouldn't be. > > I can move this if statement to the register_ftrace_export() to ensure > users won't wrongly use it, that's saying the write() of trace_export > has been set before being registered to 'ftrace_exports_list'. > Looks like it's already there: +int register_ftrace_export(struct trace_export *export) +{ + if (WARN_ON_ONCE(!export->write)) + return -1; -- Steve
diff --git a/include/linux/trace.h b/include/linux/trace.h new file mode 100644 index 0000000..eb1c5b8 --- /dev/null +++ b/include/linux/trace.h @@ -0,0 +1,28 @@ +#ifndef _LINUX_TRACE_H +#define _LINUX_TRACE_H + +#ifdef CONFIG_TRACING +/* + * The trace export - an export of Ftrace output. The trace_export + * can process traces and export them to a registered destination as + * an addition to the current only output of Ftrace - i.e. ring buffer. + * + * If you want traces to be sent to some other place rather than ring + * buffer only, just need to register a new trace_export and implement + * its own .write() function for writing traces to the storage. + * + * next - pointer to the next trace_export + * write - copy traces which have been delt with ->commit() to + * the destination + */ +struct trace_export { + struct trace_export __rcu *next; + void (*write)(const char *, unsigned int); +}; + +int register_ftrace_export(struct trace_export *export); +int unregister_ftrace_export(struct trace_export *export); + +#endif /* CONFIG_TRACING */ + +#endif /* _LINUX_TRACE_H */ diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 8696ce6..db94ec1 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -40,6 +40,7 @@ #include <linux/poll.h> #include <linux/nmi.h> #include <linux/fs.h> +#include <linux/trace.h> #include <linux/sched/rt.h> #include "trace.h" @@ -2128,6 +2129,132 @@ void trace_buffer_unlock_commit_regs(struct trace_array *tr, ftrace_trace_userstack(buffer, flags, pc); } +static void +trace_process_export(struct trace_export *export, + struct ring_buffer_event *event) +{ + struct trace_entry *entry; + unsigned int size = 0; + + entry = ring_buffer_event_data(event); + + size = ring_buffer_event_length(event); + + if (export->write) + export->write((char *)entry, size); +} + +static DEFINE_MUTEX(ftrace_export_lock); + +static struct trace_export __rcu *ftrace_exports_list __read_mostly; + +static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled); + +static inline void ftrace_exports_enable(void) +{ + static_branch_enable(&ftrace_exports_enabled); +} + +static inline void ftrace_exports_disable(void) +{ + static_branch_disable(&ftrace_exports_enabled); +} + +void ftrace_exports(struct ring_buffer_event *event) +{ + struct trace_export *export; + + preempt_disable_notrace(); + + export = rcu_dereference_raw_notrace(ftrace_exports_list); + while (export) { + trace_process_export(export, event); + export = rcu_dereference_raw_notrace(export->next); + } + + preempt_enable_notrace(); +} + +static inline void +add_trace_export(struct trace_export **list, struct trace_export *export) +{ + rcu_assign_pointer(export->next, *list); + /* + * We are entering export into the list but another + * CPU might be walking that list. We need to make sure + * the export->next pointer is valid before another CPU sees + * the export pointer included into the list. + */ + rcu_assign_pointer(*list, export); +} + +static inline int +rm_trace_export(struct trace_export **list, struct trace_export *export) +{ + struct trace_export **p; + + for (p = list; *p != NULL; p = &(*p)->next) + if (*p == export) + break; + + if (*p != export) + return -1; + + rcu_assign_pointer(*p, (*p)->next); + + return 0; +} + +static inline void +add_ftrace_export(struct trace_export **list, struct trace_export *export) +{ + if (*list == NULL) + ftrace_exports_enable(); + + add_trace_export(list, export); +} + +static inline int +rm_ftrace_export(struct trace_export **list, struct trace_export *export) +{ + int ret; + + ret = rm_trace_export(list, export); + if (*list == NULL) + ftrace_exports_disable(); + + return ret; +} + +int register_ftrace_export(struct trace_export *export) +{ + if (WARN_ON_ONCE(!export->write)) + return -1; + + mutex_lock(&ftrace_export_lock); + + add_ftrace_export(&ftrace_exports_list, export); + + mutex_unlock(&ftrace_export_lock); + + return 0; +} +EXPORT_SYMBOL_GPL(register_ftrace_export); + +int unregister_ftrace_export(struct trace_export *export) +{ + int ret; + + mutex_lock(&ftrace_export_lock); + + ret = rm_ftrace_export(&ftrace_exports_list, export); + + mutex_unlock(&ftrace_export_lock); + + return ret; +} +EXPORT_SYMBOL_GPL(unregister_ftrace_export); + void trace_function(struct trace_array *tr, unsigned long ip, unsigned long parent_ip, unsigned long flags, @@ -2146,8 +2273,11 @@ trace_function(struct trace_array *tr, entry->ip = ip; entry->parent_ip = parent_ip; - if (!call_filter_check_discard(call, entry, buffer, event)) + if (!call_filter_check_discard(call, entry, buffer, event)) { + if (static_branch_unlikely(&ftrace_exports_enabled)) + ftrace_exports(event); __buffer_unlock_commit(buffer, event); + } } #ifdef CONFIG_STACKTRACE
Currently Function traces can be only exported to ring buffer, this patch added trace_export concept which can process traces and export them to a registered destination as an addition to the current only one output of Ftrace - i.e. ring buffer. In this way, if we want Function traces to be sent to other destination rather than ring buffer only, we just need to register a new trace_export and implement its own .write() function for writing traces to storage. With this patch, only Function trace (trace type is TRACE_FN) is supported. Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org> --- include/linux/trace.h | 28 +++++++++++ kernel/trace/trace.c | 132 +++++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 159 insertions(+), 1 deletion(-) create mode 100644 include/linux/trace.h -- 2.7.4