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tracing: protect reader of cmdline output

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Impact: fix to one cause of incorrect comm outputs in trace

The spinlock only protected the creation of a comm <=> pid pair.
But it was possible that a reader could look up a pid, and get the
wrong comm because it had no locking.

This also required changing trace_find_cmdline to copy the comm cache
and not just send back a pointer to it.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
This commit is contained in:
Steven Rostedt
2009-03-16 19:20:15 -04:00
parent 03303549b1
commit 4ca5308523
5 changed files with 49 additions and 26 deletions
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23
kernel/trace/blktrace.c
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@ -1027,7 +1027,9 @@ static int blk_log_action_seq(struct trace_seq *s, const struct blk_io_trace *t,
static int blk_log_generic(struct trace_seq *s, const struct trace_entry *ent)
{
const char *cmd = trace_find_cmdline(ent->pid);
char cmd[TASK_COMM_LEN];
trace_find_cmdline(ent->pid, cmd);
if (t_sec(ent))
return trace_seq_printf(s, "%llu + %u [%s]\n",
@ -1057,19 +1059,30 @@ static int blk_log_remap(struct trace_seq *s, const struct trace_entry *ent)
static int blk_log_plug(struct trace_seq *s, const struct trace_entry *ent)
{
return trace_seq_printf(s, "[%s]\n", trace_find_cmdline(ent->pid));
char cmd[TASK_COMM_LEN];
trace_find_cmdline(ent->pid, cmd);
return trace_seq_printf(s, "[%s]\n", cmd);
}
static int blk_log_unplug(struct trace_seq *s, const struct trace_entry *ent)
{
return trace_seq_printf(s, "[%s] %llu\n", trace_find_cmdline(ent->pid),
get_pdu_int(ent));
char cmd[TASK_COMM_LEN];
trace_find_cmdline(ent->pid, cmd);
return trace_seq_printf(s, "[%s] %llu\n", cmd, get_pdu_int(ent));
}
static int blk_log_split(struct trace_seq *s, const struct trace_entry *ent)
{
char cmd[TASK_COMM_LEN];
trace_find_cmdline(ent->pid, cmd);
return trace_seq_printf(s, "%llu / %llu [%s]\n", t_sector(ent),
get_pdu_int(ent), trace_find_cmdline(ent->pid));
get_pdu_int(ent), cmd);
}
/*