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tracing: add __print_flags for events

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Developers have been asking for the ability in the ftrace event tracer
to display names of bits in a flags variable.

Instead of printing out c2, it would be easier to read FOO|BAR|GOO,
assuming that FOO is bit 1, BAR is bit 6 and GOO is bit 7.

Some examples where this would be useful are the state flags in a context
switch, kmalloc flags, and even permision flags in accessing files.

[
  v2 changes include:

  Frederic Weisbecker's idea of using a mask instead of bits,
  thus we can output GFP_KERNEL instead of GPF_WAIT|GFP_IO|GFP_FS.

  Li Zefan's idea of allowing the caller of __print_flags to add their
  own delimiter (or no delimiter) where we can get for file permissions
  rwx instead of r|w|x.
]

[
  v3 changes:

   Christoph Hellwig's idea of using an array instead of va_args.
]

[ Impact: better displaying of flags in trace output ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This commit is contained in:
Steven Rostedt 2009-05-26 20:25:22 +02:00 • committed by Frederic Weisbecker
parent 0e907c9939
commit be74b73a57
3 changed files with 65 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

39
kernel/trace/trace_output.c
View file

@ -15,6 +15,9 @@
#define EVENT_HASHSIZE 128
static DECLARE_RWSEM(trace_event_mutex);
DEFINE_PER_CPU(struct trace_seq, ftrace_event_seq);
static struct hlist_head event_hash[EVENT_HASHSIZE] __read_mostly;
static int next_event_type = __TRACE_LAST_TYPE + 1;
@ -212,6 +215,42 @@ int trace_seq_path(struct trace_seq *s, struct path *path)
return 0;
}
const char *
ftrace_print_flags_seq(struct trace_seq *p, const char *delim,
unsigned long flags,
const struct trace_print_flags *flag_array)
{
unsigned long mask;
const char *str;
int i;
trace_seq_init(p);
for (i = 0; flag_array[i].name && flags; i++) {
mask = flag_array[i].mask;
if ((flags & mask) != mask)
continue;
str = flag_array[i].name;
flags &= ~mask;
if (p->len && delim)
trace_seq_puts(p, delim);
trace_seq_puts(p, str);
}
/* check for left over flags */
if (flags) {
if (p->len && delim)
trace_seq_puts(p, delim);
trace_seq_printf(p, "0x%lx", flags);
}
trace_seq_putc(p, 0);
return p->buffer;
}
#ifdef CONFIG_KRETPROBES
static inline const char *kretprobed(const char *name)
{