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authorJoel Fernandes (Google) <joel@joelfernandes.org>2018-06-25 17:08:22 -0700
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2018-07-12 19:56:25 -0400
commitf8494fa3dd10b52eab47a9666a8bc34719a129aa (patch)
tree9ab2549656ceda99d946b69545d159ed8c1fa3d3
parent0fc8c3581dd42bc8f530314ca86db2d861485731 (diff)
tracing: Reorder display of TGID to be after PID
Currently ftrace displays data in trace output like so: _-----=> irqs-off / _----=> need-resched | / _---=> hardirq/softirq || / _--=> preempt-depth ||| / delay TASK-PID CPU TGID |||| TIMESTAMP FUNCTION | | | | |||| | | bash-1091 [000] ( 1091) d..2 28.313544: sched_switch: However Android's trace visualization tools expect a slightly different format due to an out-of-tree patch patch that was been carried for a decade, notice that the TGID and CPU fields are reversed: _-----=> irqs-off / _----=> need-resched | / _---=> hardirq/softirq || / _--=> preempt-depth ||| / delay TASK-PID TGID CPU |||| TIMESTAMP FUNCTION | | | | |||| | | bash-1091 ( 1091) [002] d..2 64.965177: sched_switch: From kernel v4.13 onwards, during which TGID was introduced, tracing with systrace on all Android kernels will break (most Android kernels have been on 4.9 with Android patches, so this issues hasn't been seen yet). From v4.13 onwards things will break. The chrome browser's tracing tools also embed the systrace viewer which uses the legacy TGID format and updates to that are known to be difficult to make. Considering this, I suggest we make this change to the upstream kernel and backport it to all Android kernels. I believe this feature is merged recently enough into the upstream kernel that it shouldn't be a problem. Also logically, IMO it makes more sense to group the TGID with the TASK-PID and the CPU after these. Link: http://lkml.kernel.org/r/20180626000822.113931-1-joel@joelfernandes.org Cc: jreck@google.com Cc: tkjos@google.com Cc: stable@vger.kernel.org Fixes: 441dae8f2f29 ("tracing: Add support for display of tgid in trace output") Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
-rw-r--r--kernel/trace/trace.c8
-rw-r--r--kernel/trace/trace_output.c5
2 files changed, 7 insertions, 6 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f054bd6a1c66..87cf25171fb8 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3365,8 +3365,8 @@ static void print_func_help_header(struct trace_buffer *buf, struct seq_file *m,
print_event_info(buf, m);
- seq_printf(m, "# TASK-PID CPU# %s TIMESTAMP FUNCTION\n", tgid ? "TGID " : "");
- seq_printf(m, "# | | | %s | |\n", tgid ? " | " : "");
+ seq_printf(m, "# TASK-PID %s CPU# TIMESTAMP FUNCTION\n", tgid ? "TGID " : "");
+ seq_printf(m, "# | | %s | | |\n", tgid ? " | " : "");
}
static void print_func_help_header_irq(struct trace_buffer *buf, struct seq_file *m,
@@ -3386,9 +3386,9 @@ static void print_func_help_header_irq(struct trace_buffer *buf, struct seq_file
tgid ? tgid_space : space);
seq_printf(m, "# %s||| / delay\n",
tgid ? tgid_space : space);
- seq_printf(m, "# TASK-PID CPU#%s|||| TIMESTAMP FUNCTION\n",
+ seq_printf(m, "# TASK-PID %sCPU# |||| TIMESTAMP FUNCTION\n",
tgid ? " TGID " : space);
- seq_printf(m, "# | | | %s|||| | |\n",
+ seq_printf(m, "# | | %s | |||| | |\n",
tgid ? " | " : space);
}
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 90db994ac900..1c8e30fda46a 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -594,8 +594,7 @@ int trace_print_context(struct trace_iterator *iter)
trace_find_cmdline(entry->pid, comm);
- trace_seq_printf(s, "%16s-%-5d [%03d] ",
- comm, entry->pid, iter->cpu);
+ trace_seq_printf(s, "%16s-%-5d ", comm, entry->pid);
if (tr->trace_flags & TRACE_ITER_RECORD_TGID) {
unsigned int tgid = trace_find_tgid(entry->pid);
@@ -606,6 +605,8 @@ int trace_print_context(struct trace_iterator *iter)
trace_seq_printf(s, "(%5d) ", tgid);
}
+ trace_seq_printf(s, "[%03d] ", iter->cpu);
+
if (tr->trace_flags & TRACE_ITER_IRQ_INFO)
trace_print_lat_fmt(s, entry);