mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-12 13:55:32 +00:00
![Steven Rostedt](/assets/img/avatar_default.png)
If the seq_read fills the buffer it will call s_start again on the next itertation with the same position. This causes a problem with the function_graph tracer because it consumes the iteration in order to determine leaf functions. What happens is that the iterator stores the entry, and the function graph plugin will look at the next entry. If that next entry is a return of the same function and task, then the function is a leaf and the function_graph plugin calls ring_buffer_read which moves the ring buffer iterator forward (the trace iterator still points to the function start entry). The copying of the trace_seq to the seq_file buffer will fail if the seq_file buffer is full. The seq_read will not show this entry. The next read by userspace will cause seq_read to again call s_start which will reuse the trace iterator entry (the function start entry). But the function return entry was already consumed. The function graph plugin will think that this entry is a nested function and not a leaf. To solve this, the trace code now checks the return status of the seq_printf (trace_print_seq). If the writing to the seq_file buffer fails, we set a flag in the iterator (leftover) and we do not reset the trace_seq buffer. On the next call to s_start, we check the leftover flag, and if it is set, we just reuse the trace_seq buffer and do not call into the plugin print functions. Before this patch: 2) | fput() { 2) | __fput() { 2) 0.550 us | inotify_inode_queue_event(); 2) | __fsnotify_parent() { 2) 0.540 us | inotify_dentry_parent_queue_event(); After the patch: 2) | fput() { 2) | __fput() { 2) 0.550 us | inotify_inode_queue_event(); 2) 0.548 us | __fsnotify_parent(); 2) 0.540 us | inotify_dentry_parent_queue_event(); [ Updated the patch to fix a missing return 0 from the trace_print_seq() stub when CONFIG_TRACING is disabled. Reported-by: Ingo Molnar <mingo@elte.hu> ] Reported-by: Jiri Olsa <jolsa@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
95 lines
2.4 KiB
C
95 lines
2.4 KiB
C
#ifndef _LINUX_TRACE_SEQ_H
|
|
#define _LINUX_TRACE_SEQ_H
|
|
|
|
#include <linux/fs.h>
|
|
|
|
#include <asm/page.h>
|
|
|
|
/*
|
|
* Trace sequences are used to allow a function to call several other functions
|
|
* to create a string of data to use (up to a max of PAGE_SIZE).
|
|
*/
|
|
|
|
struct trace_seq {
|
|
unsigned char buffer[PAGE_SIZE];
|
|
unsigned int len;
|
|
unsigned int readpos;
|
|
};
|
|
|
|
static inline void
|
|
trace_seq_init(struct trace_seq *s)
|
|
{
|
|
s->len = 0;
|
|
s->readpos = 0;
|
|
}
|
|
|
|
/*
|
|
* Currently only defined when tracing is enabled.
|
|
*/
|
|
#ifdef CONFIG_TRACING
|
|
extern int trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
|
|
__attribute__ ((format (printf, 2, 3)));
|
|
extern int trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
|
|
__attribute__ ((format (printf, 2, 0)));
|
|
extern int
|
|
trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary);
|
|
extern int trace_print_seq(struct seq_file *m, struct trace_seq *s);
|
|
extern ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
|
|
size_t cnt);
|
|
extern int trace_seq_puts(struct trace_seq *s, const char *str);
|
|
extern int trace_seq_putc(struct trace_seq *s, unsigned char c);
|
|
extern int trace_seq_putmem(struct trace_seq *s, const void *mem, size_t len);
|
|
extern int trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
|
|
size_t len);
|
|
extern void *trace_seq_reserve(struct trace_seq *s, size_t len);
|
|
extern int trace_seq_path(struct trace_seq *s, struct path *path);
|
|
|
|
#else /* CONFIG_TRACING */
|
|
static inline int trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline int
|
|
trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline int trace_print_seq(struct seq_file *m, struct trace_seq *s)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
|
|
size_t cnt)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline int trace_seq_puts(struct trace_seq *s, const char *str)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline int trace_seq_putc(struct trace_seq *s, unsigned char c)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline int
|
|
trace_seq_putmem(struct trace_seq *s, const void *mem, size_t len)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline int trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
|
|
size_t len)
|
|
{
|
|
return 0;
|
|
}
|
|
static inline void *trace_seq_reserve(struct trace_seq *s, size_t len)
|
|
{
|
|
return NULL;
|
|
}
|
|
static inline int trace_seq_path(struct trace_seq *s, struct path *path)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif /* CONFIG_TRACING */
|
|
|
|
#endif /* _LINUX_TRACE_SEQ_H */
|