4.17-stable review patch. If anyone has any objections, please let me know.
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From: Joel Fernandes (Google) joel@joelfernandes.org
commit f8494fa3dd10b52eab47a9666a8bc34719a129aa upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/trace/trace.c | 8 ++++---- kernel/trace/trace_output.c | 5 +++-- 2 files changed, 7 insertions(+), 6 deletions(-)
--- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3363,8 +3363,8 @@ static void print_func_help_header(struc
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, @@ -3384,9 +3384,9 @@ static void print_func_help_header_irq(s 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); }
--- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -594,8 +594,7 @@ int trace_print_context(struct trace_ite
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_ite 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);