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tracing: Fix lock inversion in trace_event_enable_tgid_record()

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Task T2                             Task T3
trace_options_core_write()            subsystem_open()

 mutex_lock(trace_types_lock)           mutex_lock(event_mutex)

 set_tracer_flag()

   trace_event_enable_tgid_record()       mutex_lock(trace_types_lock)

    mutex_lock(event_mutex)

This gives a circular dependency deadlock between trace_types_lock and
event_mutex. To fix this invert the usage of trace_types_lock and
event_mutex in trace_options_core_write(). This keeps the sequence of
lock usage consistent.

Change-Id: Ide261e25fb15f79391a6220eef246e274b0c6a69
Signed-off-by: Prateek Sood <prsood@codeaurora.org>
This commit is contained in:
Prateek Sood 2019-12-23 10:49:46 +05:30 committed by Gerrit - the friendly Code Review server
parent f4e38462ed
commit ad677f2848
2 changed files with 12 additions and 4 deletions
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8
kernel/trace/trace.c
View file

@ -4376,6 +4376,10 @@ int trace_keep_overwrite(struct tracer *tracer, u32 mask, int set)
int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled)
{
if ((mask == TRACE_ITER_RECORD_TGID) ||
(mask == TRACE_ITER_RECORD_CMD))
lockdep_assert_held(&event_mutex);
/* do nothing if flag is already set */
if (!!(tr->trace_flags & mask) == !!enabled)
return 0;
@ -4441,6 +4445,7 @@ static int trace_set_options(struct trace_array *tr, char *option)
cmp += 2;
}
mutex_lock(&event_mutex);
mutex_lock(&trace_types_lock);
ret = match_string(trace_options, -1, cmp);
@ -4451,6 +4456,7 @@ static int trace_set_options(struct trace_array *tr, char *option)
ret = set_tracer_flag(tr, 1 << ret, !neg);
mutex_unlock(&trace_types_lock);
mutex_unlock(&event_mutex);
/*
* If the first trailing whitespace is replaced with '\0' by strstrip,
@ -7467,9 +7473,11 @@ trace_options_core_write(struct file *filp, const char __user *ubuf, size_t cnt,
if (val != 0 && val != 1)
return -EINVAL;
mutex_lock(&event_mutex);
mutex_lock(&trace_types_lock);
ret = set_tracer_flag(tr, 1 << index, val);
mutex_unlock(&trace_types_lock);
mutex_unlock(&event_mutex);
if (ret < 0)
return ret;

8
kernel/trace/trace_events.c
View file

@ -327,7 +327,8 @@ void trace_event_enable_cmd_record(bool enable)
struct trace_event_file *file;
struct trace_array *tr;
mutex_lock(&event_mutex);
lockdep_assert_held(&event_mutex);
do_for_each_event_file(tr, file) {
if (!(file->flags & EVENT_FILE_FL_ENABLED))
@ -341,7 +342,6 @@ void trace_event_enable_cmd_record(bool enable)
clear_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags);
}
} while_for_each_event_file();
mutex_unlock(&event_mutex);
}
void trace_event_enable_tgid_record(bool enable)
@ -349,7 +349,8 @@ void trace_event_enable_tgid_record(bool enable)
struct trace_event_file *file;
struct trace_array *tr;
mutex_lock(&event_mutex);
lockdep_assert_held(&event_mutex);
do_for_each_event_file(tr, file) {
if (!(file->flags & EVENT_FILE_FL_ENABLED))
continue;
@ -363,7 +364,6 @@ void trace_event_enable_tgid_record(bool enable)
&file->flags);
}
} while_for_each_event_file();
mutex_unlock(&event_mutex);
}
static int __ftrace_event_enable_disable(struct trace_event_file *file,