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author | Jiri Olsa <jolsa@redhat.com> | 2011-03-25 12:05:18 +0100 |
---|---|---|
committer | Steven Rostedt <rostedt@goodmis.org> | 2011-04-04 12:18:24 -0400 |
commit | ee5e51f51be755830f57445e268ba50e88ccbdbb (patch) | |
tree | 059d6c5843275a5ab94ae01408c1dc6dbe00b2ea /kernel/trace/trace_output.c | |
parent | 1813dc3776c22ad4b0294a6df8434b9a02c98109 (diff) | |
download | linux-ee5e51f51be755830f57445e268ba50e88ccbdbb.tar.bz2 |
tracing: Avoid soft lockup in trace_pipe
running following commands:
# enable the binary option
echo 1 > ./options/bin
# disable context info option
echo 0 > ./options/context-info
# tracing only events
echo 1 > ./events/enable
cat trace_pipe
plus forcing system to generate many tracing events,
is causing lockup (in NON preemptive kernels) inside
tracing_read_pipe function.
The issue is also easily reproduced by running ltp stress test.
(ftrace_stress_test.sh)
The reasons are:
- bin/hex/raw output functions for events are set to
trace_nop_print function, which prints nothing and
returns TRACE_TYPE_HANDLED value
- LOST EVENT trace do not handle trace_seq overflow
These reasons force the while loop in tracing_read_pipe
function never to break.
The attached patch fixies handling of lost event trace, and
changes trace_nop_print to print minimal info, which is needed
for the correct tracing_read_pipe processing.
v2 changes:
- omit the cond_resched changes by trace_nop_print changes
- WARN changed to WARN_ONCE and added info to be able
to find out the culprit
v3 changes:
- make more accurate patch comment
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
LKML-Reference: <20110325110518.GC1922@jolsa.brq.redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace_output.c')
-rw-r--r-- | kernel/trace/trace_output.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 456be9063c2d..cf535ccedc86 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -830,6 +830,9 @@ EXPORT_SYMBOL_GPL(unregister_ftrace_event); enum print_line_t trace_nop_print(struct trace_iterator *iter, int flags, struct trace_event *event) { + if (!trace_seq_printf(&iter->seq, "type: %d\n", iter->ent->type)) + return TRACE_TYPE_PARTIAL_LINE; + return TRACE_TYPE_HANDLED; } |