[tip:tracing/tasks] tracing: replace the crude (unsigned) -1 hackery

Thomas Gleixner
2009-03-18T09:19:49Z

Commit-ID: 2c7eea4c62ba090b7f4583c3d7337ea0019be900
Gitweb: http://git.kernel.org/tip/2c7eea4c62ba090b7f4583c3d7337ea0019be900
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 18 Mar 2009 09:03:19 +0100
Commit: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 18 Mar 2009 10:10:17 +0100

tracing: replace the crude (unsigned) -1 hackery

Impact: cleanup

The command line recorder uses (unsigned) -1 to mark non mapped
entries in the pid to command line maps. The validity check is
completely unintuitive: idx >= SAVED_CMDLINES

There is no need for such casting games. Use a constant to mark
unmapped entries and check for that constant to make the code readable
and understandable.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
kernel/trace/trace.c | 13 +++++++------
1 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7b6043e..ca673c4 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -633,6 +633,7 @@ void tracing_reset_online_cpus(struct trace_array *tr)
}

#define SAVED_CMDLINES 128
+#define NO_CMDLINE_MAP UINT_MAX
static unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
static unsigned map_cmdline_to_pid[SAVED_CMDLINES];
static char saved_cmdlines[SAVED_CMDLINES][TASK_COMM_LEN];
@@ -644,8 +645,8 @@ static atomic_t trace_record_cmdline_disabled __read_mostly;

static void trace_init_cmdlines(void)
{
- memset(&map_pid_to_cmdline, -1, sizeof(map_pid_to_cmdline));
- memset(&map_cmdline_to_pid, -1, sizeof(map_cmdline_to_pid));
+ memset(&map_pid_to_cmdline, NO_CMDLINE_MAP, sizeof(map_pid_to_cmdline));
+ memset(&map_cmdline_to_pid, NO_CMDLINE_MAP, sizeof(map_cmdline_to_pid));
cmdline_idx = 0;
}

@@ -753,12 +754,12 @@ static void trace_save_cmdline(struct task_struct *tsk)
return;

idx = map_pid_to_cmdline[tsk->pid];
- if (idx >= SAVED_CMDLINES) {
+ if (idx == NO_CMDLINE_MAP) {
idx = (cmdline_idx + 1) % SAVED_CMDLINES;

map = map_cmdline_to_pid[idx];
- if (map <= PID_MAX_DEFAULT)
- map_pid_to_cmdline[map] = (unsigned)-1;
+ if (map != NO_CMDLINE_MAP)
+ map_pid_to_cmdline[map] = NO_CMDLINE_MAP;

map_pid_to_cmdline[tsk->pid] = idx;

@@ -786,7 +787,7 @@ void trace_find_cmdline(int pid, char comm[])

__raw_spin_lock(&trace_cmdline_lock);
map = map_pid_to_cmdline[pid];
- if (map >= SAVED_CMDLINES)
+ if (map == NO_CMDLINE_MAP)
goto out;

strcpy(comm, saved_cmdlines[map]);