From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: [for-next][PATCH 16/21] ftrace: Make function trace pid filtering a bit more exact
Date: Sun, 29 Mar 2020 14:43:08 -0400 [thread overview]
Message-ID: <20200329184317.785657014@goodmis.org> (raw)
In-Reply-To: 20200329184252.289087453@goodmis.org
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
The set_ftrace_pid file is used to filter function tracing to only trace
tasks that are listed in that file. Instead of testing the pids listed in
that file (it's a bitmask) at each function trace event, the logic is done
via a sched_switch hook. A flag is set when the next task to run is in the
list of pids in the set_ftrace_pid file. But the sched_switch hook is not at
the exact location of when the task switches, and the flag gets set before
the task to be traced actually runs. This leaves a residue of traced
functions that do not belong to the pid that should be filtered on.
By changing the logic slightly, where instead of having a boolean flag to
test, record the pid that should be traced, with special values for not to
trace and always trace. Then at each function call, a check will be made to
see if the function should be ignored, or if the current pid matches the
function that should be traced, and only trace if it matches (or if it has
the special value to always trace).
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/ftrace.c | 32 +++++++++++++++++++++++++-------
kernel/trace/trace.h | 4 ++--
2 files changed, 27 insertions(+), 9 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 3f7ee102868a..34ae736cb1f8 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -139,13 +139,23 @@ static inline void ftrace_ops_init(struct ftrace_ops *ops)
#endif
}
+#define FTRACE_PID_IGNORE -1
+#define FTRACE_PID_TRACE -2
+
static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct pt_regs *regs)
{
struct trace_array *tr = op->private;
+ int pid;
- if (tr && this_cpu_read(tr->array_buffer.data->ftrace_ignore_pid))
- return;
+ if (tr) {
+ pid = this_cpu_read(tr->array_buffer.data->ftrace_ignore_pid);
+ if (pid == FTRACE_PID_IGNORE)
+ return;
+ if (pid != FTRACE_PID_TRACE &&
+ pid != current->pid)
+ return;
+ }
op->saved_func(ip, parent_ip, op, regs);
}
@@ -6924,8 +6934,12 @@ ftrace_filter_pid_sched_switch_probe(void *data, bool preempt,
pid_list = rcu_dereference_sched(tr->function_pids);
- this_cpu_write(tr->array_buffer.data->ftrace_ignore_pid,
- trace_ignore_this_task(pid_list, next));
+ if (trace_ignore_this_task(pid_list, next))
+ this_cpu_write(tr->array_buffer.data->ftrace_ignore_pid,
+ FTRACE_PID_IGNORE);
+ else
+ this_cpu_write(tr->array_buffer.data->ftrace_ignore_pid,
+ next->pid);
}
static void
@@ -6978,7 +6992,7 @@ static void clear_ftrace_pids(struct trace_array *tr)
unregister_trace_sched_switch(ftrace_filter_pid_sched_switch_probe, tr);
for_each_possible_cpu(cpu)
- per_cpu_ptr(tr->array_buffer.data, cpu)->ftrace_ignore_pid = false;
+ per_cpu_ptr(tr->array_buffer.data, cpu)->ftrace_ignore_pid = FTRACE_PID_TRACE;
rcu_assign_pointer(tr->function_pids, NULL);
@@ -7103,8 +7117,12 @@ static void ignore_task_cpu(void *data)
pid_list = rcu_dereference_protected(tr->function_pids,
mutex_is_locked(&ftrace_lock));
- this_cpu_write(tr->array_buffer.data->ftrace_ignore_pid,
- trace_ignore_this_task(pid_list, current));
+ if (trace_ignore_this_task(pid_list, current))
+ this_cpu_write(tr->array_buffer.data->ftrace_ignore_pid,
+ FTRACE_PID_IGNORE);
+ else
+ this_cpu_write(tr->array_buffer.data->ftrace_ignore_pid,
+ current->pid);
}
static ssize_t
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f37e05135986..fdc72f5f0bb0 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -178,10 +178,10 @@ struct trace_array_cpu {
kuid_t uid;
char comm[TASK_COMM_LEN];
- bool ignore_pid;
#ifdef CONFIG_FUNCTION_TRACER
- bool ftrace_ignore_pid;
+ int ftrace_ignore_pid;
#endif
+ bool ignore_pid;
};
struct tracer;
--
2.25.1
next prev parent reply other threads:[~2020-03-29 18:44 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-29 18:42 [for-next][PATCH 00/21] tracing: Updates for v5.7 Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 01/21] tracing: Use address-of operator on section symbols Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 02/21] selftest/ftrace: Fix function trigger test to handle trace not disabling the tracer Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 03/21] tracing: Save off entry when peeking at next entry Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 04/21] ring-buffer: Have ring_buffer_empty() not depend on tracing stopped Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 05/21] ring-buffer: Rename ring_buffer_read() to read_buffer_iter_advance() Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 06/21] ring-buffer: Add page_stamp to iterator for synchronization Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 07/21] ring-buffer: Have rb_iter_head_event() handle concurrent writer Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 08/21] ring-buffer: Do not die if rb_iter_peek() fails more than thrice Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 09/21] ring-buffer: Optimize rb_iter_head_event() Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 10/21] ring-buffer: Make resize disable per cpu buffer instead of total buffer Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 11/21] ring-buffer: Do not disable recording when there is an iterator Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 12/21] tracing: Do not disable tracing when reading the trace file Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 13/21] ring-buffer/tracing: Have iterator acknowledge dropped events Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 14/21] tracing: Have the document reflect that the trace file keeps tracing enabled Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 15/21] ftrace/kprobe: Show the maxactive number on kprobe_events Steven Rostedt
2020-03-31 13:11 ` Sasha Levin
2020-03-29 18:43 ` Steven Rostedt [this message]
2020-03-29 18:43 ` [for-next][PATCH 17/21] ftrace: Create set_ftrace_notrace_pid to not trace tasks Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 18/21] tracing: Create set_event_notrace_pid " Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 19/21] selftests/ftrace: Add test to test new set_ftrace_notrace_pid file Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 20/21] selftests/ftrace: Add test to test new set_event_notrace_pid file Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 21/21] tracing: Add documentation on set_ftrace_notrace_pid and set_event_notrace_pid Steven Rostedt
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