(2013/06/14 10:44), zhangwei(Jovi) wrote: > Support multi-buffer on uprobe-based dynamic events by > using ftrace_event_file. > > The code change is based on kprobe-based dynamic events > multibuffer support work commited by Masami(commit 41a7dd420c)
I'm not so sure that rcu_dereference_raw() can ensure the safety of accessing pointer in uprobe handler. ( since kprobes disables irq and preempt, it could use rcu.) Srikar, Oleg, could you check that? Thank you, > > Signed-off-by: zhangwei(Jovi) <[email protected]> > Cc: Masami Hiramatsu <[email protected]> > Cc: Frederic Weisbecker <[email protected]> > Cc: Oleg Nesterov <[email protected]> > Cc: Srikar Dronamraju <[email protected]> > --- > kernel/trace/trace_uprobe.c | 183 > +++++++++++++++++++++++++++++++++++++------ > 1 file changed, 161 insertions(+), 22 deletions(-) > > diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c > index d5d0cd3..31f08d6 100644 > --- a/kernel/trace/trace_uprobe.c > +++ b/kernel/trace/trace_uprobe.c > @@ -53,6 +53,7 @@ struct trace_uprobe { > struct list_head list; > struct ftrace_event_class class; > struct ftrace_event_call call; > + struct ftrace_event_file * __rcu *files; > struct trace_uprobe_filter filter; > struct uprobe_consumer consumer; > struct inode *inode; > @@ -513,7 +514,8 @@ static const struct file_operations uprobe_profile_ops = { > }; > > static void uprobe_trace_print(struct trace_uprobe *tu, > - unsigned long func, struct pt_regs *regs) > + unsigned long func, struct pt_regs *regs, > + struct ftrace_event_file *ftrace_file) > { > struct uprobe_trace_entry_head *entry; > struct ring_buffer_event *event; > @@ -522,9 +524,15 @@ static void uprobe_trace_print(struct trace_uprobe *tu, > int size, i; > struct ftrace_event_call *call = &tu->call; > > + WARN_ON(call != ftrace_file->event_call); > + > + if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &ftrace_file->flags)) > + return; > + > size = SIZEOF_TRACE_ENTRY(is_ret_probe(tu)); > - event = trace_current_buffer_lock_reserve(&buffer, call->event.type, > - size + tu->size, 0, 0); > + event = trace_event_buffer_lock_reserve(&buffer, ftrace_file, > + call->event.type, > + size + tu->size, 0, 0); > if (!event) > return; > > @@ -548,15 +556,35 @@ static void uprobe_trace_print(struct trace_uprobe *tu, > /* uprobe handler */ > static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs) > { > - if (!is_ret_probe(tu)) > - uprobe_trace_print(tu, 0, regs); > + struct ftrace_event_file **file; > + > + if (is_ret_probe(tu)) > + return 0; > + > + file = rcu_dereference_raw(tu->files); > + if (unlikely(!file)) > + return 0; > + > + while (*file) { > + uprobe_trace_print(tu, 0, regs, *file); > + file++; > + } > + > return 0; > } > > static void uretprobe_trace_func(struct trace_uprobe *tu, unsigned long func, > struct pt_regs *regs) > { > - uprobe_trace_print(tu, func, regs); > + struct ftrace_event_file **file = rcu_dereference_raw(tu->files); > + > + if (unlikely(!file)) > + return; > + > + while (*file) { > + uprobe_trace_print(tu, func, regs, *file); > + file++; > + } > } > > /* Event entry printers */ > @@ -597,6 +625,26 @@ partial: > return TRACE_TYPE_PARTIAL_LINE; > } > > + > +static int trace_uprobe_nr_files(struct trace_uprobe *tu) > +{ > + struct ftrace_event_file **file; > + int ret = 0; > + > + /* > + * Since all tu->files updater is protected by uprobe_enable_lock, > + * we don't need to lock an rcu_read_lock. > + */ > + file = rcu_dereference_raw(tu->files); > + if (file) > + while (*(file++)) > + ret++; > + > + return ret; > +} > + > +static DEFINE_MUTEX(uprobe_enable_lock); > + > static inline bool is_trace_uprobe_enabled(struct trace_uprobe *tu) > { > return tu->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE); > @@ -607,33 +655,123 @@ typedef bool (*filter_func_t)(struct uprobe_consumer > *self, > struct mm_struct *mm); > > static int > -probe_event_enable(struct trace_uprobe *tu, int flag, filter_func_t filter) > +probe_event_enable(struct trace_uprobe *tu, struct ftrace_event_file *file, > + filter_func_t filter) > { > + int enabled = 0; > int ret = 0; > > + mutex_lock(&uprobe_enable_lock); > + > if (is_trace_uprobe_enabled(tu)) > - return -EINTR; > + enabled = 1; > + > + if (file) { > + struct ftrace_event_file **new, **old; > + int n = trace_uprobe_nr_files(tu); > + > + old = rcu_dereference_raw(tu->files); > + /* 1 is for new one and 1 is for stopper */ > + new = kzalloc((n + 2) * sizeof(struct ftrace_event_file *), > + GFP_KERNEL); > + if (!new) { > + ret = -ENOMEM; > + goto out_unlock; > + } > + memcpy(new, old, n * sizeof(struct ftrace_event_file *)); > + new[n] = file; > + /* The last one keeps a NULL */ > + > + rcu_assign_pointer(tu->files, new); > + tu->flags |= TP_FLAG_TRACE; > + > + if (old) { > + /* Make sure the probe is done with old files */ > + synchronize_sched(); > + kfree(old); > + } > + } else > + tu->flags |= TP_FLAG_PROFILE; > > WARN_ON(!uprobe_filter_is_empty(&tu->filter)); > > - tu->flags |= flag; > - tu->consumer.filter = filter; > - ret = uprobe_register(tu->inode, tu->offset, &tu->consumer); > - if (ret) > - tu->flags &= ~flag; > + if (!enabled) { > + tu->consumer.filter = filter; > + ret = uprobe_register(tu->inode, tu->offset, &tu->consumer); > + if (ret) > + tu->flags &= file ? ~TP_FLAG_TRACE : ~TP_FLAG_PROFILE; > + } > > + out_unlock: > + mutex_unlock(&uprobe_enable_lock); > return ret; > } > > -static void probe_event_disable(struct trace_uprobe *tu, int flag) > +static int > +trace_uprobe_file_index(struct trace_uprobe *tu, struct ftrace_event_file > *file) > { > - if (!is_trace_uprobe_enabled(tu)) > - return; > + struct ftrace_event_file **files; > + int i; > + > + /* > + * Since all tu->files updater is protected by uprobe_enable_lock, > + * we don't need to lock an rcu_read_lock. > + */ > + files = rcu_dereference_raw(tu->files); > + if (files) { > + for (i = 0; files[i]; i++) > + if (files[i] == file) > + return i; > + } > + > + return -1; > +} > + > +static void > +probe_event_disable(struct trace_uprobe *tu, struct ftrace_event_file *file) > +{ > + mutex_lock(&uprobe_enable_lock); > + > + if (file) { > + struct ftrace_event_file **new, **old; > + int n = trace_uprobe_nr_files(tu); > + int i, j; > + > + old = rcu_dereference_raw(tu->files); > + if (n == 0 || trace_uprobe_file_index(tu, file) < 0) > + goto out_unlock; > + > + if (n == 1) { /* Remove the last file */ > + tu->flags &= ~TP_FLAG_TRACE; > + new = NULL; > + } else { > + new = kzalloc(n * sizeof(struct ftrace_event_file *), > + GFP_KERNEL); > + if (!new) > + goto out_unlock; > + > + /* This copy & check loop copies the NULL stopper too */ > + for (i = 0, j = 0; j < n && i < n + 1; i++) > + if (old[i] != file) > + new[j++] = old[i]; > + } > + > + rcu_assign_pointer(tu->files, new); > + > + /* Make sure the probe is done with old files */ > + synchronize_sched(); > + kfree(old); > + } else > + tu->flags &= ~TP_FLAG_PROFILE; > + > > WARN_ON(!uprobe_filter_is_empty(&tu->filter)); > > - uprobe_unregister(tu->inode, tu->offset, &tu->consumer); > - tu->flags &= ~flag; > + if (!is_trace_uprobe_enabled(tu)) > + uprobe_unregister(tu->inode, tu->offset, &tu->consumer); > + > + out_unlock: > + mutex_unlock(&uprobe_enable_lock); > } > > static int uprobe_event_define_fields(struct ftrace_event_call *event_call) > @@ -869,21 +1007,22 @@ static > int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg > type, void *data) > { > struct trace_uprobe *tu = event->data; > + struct ftrace_event_file *file = data; > > switch (type) { > case TRACE_REG_REGISTER: > - return probe_event_enable(tu, TP_FLAG_TRACE, NULL); > + return probe_event_enable(tu, file, NULL); > > case TRACE_REG_UNREGISTER: > - probe_event_disable(tu, TP_FLAG_TRACE); > + probe_event_disable(tu, file); > return 0; > > #ifdef CONFIG_PERF_EVENTS > case TRACE_REG_PERF_REGISTER: > - return probe_event_enable(tu, TP_FLAG_PROFILE, > uprobe_perf_filter); > + return probe_event_enable(tu, NULL, uprobe_perf_filter); > > case TRACE_REG_PERF_UNREGISTER: > - probe_event_disable(tu, TP_FLAG_PROFILE); > + probe_event_disable(tu, NULL); > return 0; > > case TRACE_REG_PERF_OPEN: > -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: [email protected] -- 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/
