| Message ID | 20230713114626.704ebe8e@gandalf.local.home (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | tracing: Clean up how iter is freed | expand |
On Thu, 13 Jul 2023 11:46:26 -0400 Steven Rostedt <rostedt@goodmis.org> wrote: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > I have no idea why the iterator had to allocate a descriptor to make a > copy of "current_trace" (now "tr->current_trace"). The content of that > pointer never changes, so it's sufficient to just copy the pointer to > maintain integrity with reading it. > > This is more of a clean up than a fix. Interesting bug. Anyway looks good to me. Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Thank you, > > Fixes: d7350c3f45694 ("tracing/core: make the read callbacks reentrants") > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > --- > kernel/trace/trace.c | 22 +++------------------- > 1 file changed, 3 insertions(+), 19 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index be847d45d81c..1c370ffbe062 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -4205,15 +4205,9 @@ static void *s_start(struct seq_file *m, loff_t *pos) > loff_t l = 0; > int cpu; > > - /* > - * copy the tracer to avoid using a global lock all around. > - * iter->trace is a copy of current_trace, the pointer to the > - * name may be used instead of a strcmp(), as iter->trace->name > - * will point to the same string as current_trace->name. > - */ > mutex_lock(&trace_types_lock); > - if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name)) > - *iter->trace = *tr->current_trace; > + if (unlikely(tr->current_trace != iter->trace)) > + iter->trace = tr->current_trace; > mutex_unlock(&trace_types_lock); > > #ifdef CONFIG_TRACER_MAX_TRACE > @@ -4862,16 +4856,8 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot) > iter->fmt = NULL; > iter->fmt_size = 0; > > - /* > - * We make a copy of the current tracer to avoid concurrent > - * changes on it while we are reading. > - */ > mutex_lock(&trace_types_lock); > - iter->trace = kzalloc(sizeof(*iter->trace), GFP_KERNEL); > - if (!iter->trace) > - goto fail; > - > - *iter->trace = *tr->current_trace; > + iter->trace = tr->current_trace; > > if (!zalloc_cpumask_var(&iter->started, GFP_KERNEL)) > goto fail; > @@ -4936,7 +4922,6 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot) > > fail: > mutex_unlock(&trace_types_lock); > - kfree(iter->trace); > kfree(iter->temp); > kfree(iter->buffer_iter); > release: > @@ -5021,7 +5006,6 @@ static int tracing_release(struct inode *inode, struct file *file) > free_cpumask_var(iter->started); > kfree(iter->fmt); > kfree(iter->temp); > - kfree(iter->trace); > kfree(iter->buffer_iter); > seq_release_private(inode, file); > > -- > 2.40.1 >
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index be847d45d81c..1c370ffbe062 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4205,15 +4205,9 @@ static void *s_start(struct seq_file *m, loff_t *pos) loff_t l = 0; int cpu; - /* - * copy the tracer to avoid using a global lock all around. - * iter->trace is a copy of current_trace, the pointer to the - * name may be used instead of a strcmp(), as iter->trace->name - * will point to the same string as current_trace->name. - */ mutex_lock(&trace_types_lock); - if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name)) - *iter->trace = *tr->current_trace; + if (unlikely(tr->current_trace != iter->trace)) + iter->trace = tr->current_trace; mutex_unlock(&trace_types_lock); #ifdef CONFIG_TRACER_MAX_TRACE @@ -4862,16 +4856,8 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot) iter->fmt = NULL; iter->fmt_size = 0; - /* - * We make a copy of the current tracer to avoid concurrent - * changes on it while we are reading. - */ mutex_lock(&trace_types_lock); - iter->trace = kzalloc(sizeof(*iter->trace), GFP_KERNEL); - if (!iter->trace) - goto fail; - - *iter->trace = *tr->current_trace; + iter->trace = tr->current_trace; if (!zalloc_cpumask_var(&iter->started, GFP_KERNEL)) goto fail; @@ -4936,7 +4922,6 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot) fail: mutex_unlock(&trace_types_lock); - kfree(iter->trace); kfree(iter->temp); kfree(iter->buffer_iter); release: @@ -5021,7 +5006,6 @@ static int tracing_release(struct inode *inode, struct file *file) free_cpumask_var(iter->started); kfree(iter->fmt); kfree(iter->temp); - kfree(iter->trace); kfree(iter->buffer_iter); seq_release_private(inode, file);