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Merge "Do not set properties in bionic_systrace"

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Tom Cherry 2015-12-10 23:05:15 +00:00 committed by Gerrit Code Review
commit e46ded5ce1
1 changed files with 14 additions and 16 deletions
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30
libc/bionic/bionic_systrace.cpp
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@ -34,27 +34,25 @@ constexpr char SYSTRACE_PROPERTY_NAME[] = "debug.atrace.tags.enableflags";
static Lock g_lock; static Lock g_lock;
static const prop_info* g_pinfo; static const prop_info* g_pinfo;
static uint32_t g_serial = -1; static uint32_t g_property_serial = -1;
static uint32_t g_property_area_serial = -1;
static uint64_t g_tags; static uint64_t g_tags;
static int g_trace_marker_fd = -1; static int g_trace_marker_fd = -1;
static bool should_trace() { static bool should_trace() {
bool result = false; bool result = false;
g_lock.lock(); g_lock.lock();
// If g_pinfo is null, this means that systrace hasn't been run and it's safe to // debug.atrace.tags.enableflags is set to a safe non-tracing value during property
// assume that no trace writing will need to take place. However, to avoid running // space initialization, so it should only be null in two cases, if there are
// this costly find check each time, we set it to a non-tracing value so that next // insufficient permissions for this process to access the property, in which
// time, it will just check the serial to see if the value has been changed. // case an audit will be logged, and during boot before the property server has
// this function also deals with the bootup case, during which the call to property // been started, in which case we store the global property_area serial to prevent
// set will fail if the property server hasn't yet started. // the costly find operation until we see a changed property_area.
if (g_pinfo == NULL) { if (!g_pinfo && g_property_area_serial != __system_property_area_serial()) {
g_property_area_serial = __system_property_area_serial();
g_pinfo = __system_property_find(SYSTRACE_PROPERTY_NAME); g_pinfo = __system_property_find(SYSTRACE_PROPERTY_NAME);
if (g_pinfo == NULL) {
__system_property_set(SYSTRACE_PROPERTY_NAME, "0");
g_pinfo = __system_property_find(SYSTRACE_PROPERTY_NAME);
}
} }
if (g_pinfo != NULL) { if (g_pinfo) {
// Find out which tags have been enabled on the command line and set // Find out which tags have been enabled on the command line and set
// the value of tags accordingly. If the value of the property changes, // the value of tags accordingly. If the value of the property changes,
// the serial will also change, so the costly system_property_read function // the serial will also change, so the costly system_property_read function
@ -62,11 +60,11 @@ static bool should_trace() {
// first. The values within pinfo may change, but its location is guaranteed // first. The values within pinfo may change, but its location is guaranteed
// not to move. // not to move.
uint32_t cur_serial = __system_property_serial(g_pinfo); uint32_t cur_serial = __system_property_serial(g_pinfo);
if (cur_serial != g_serial) { if (cur_serial != g_property_serial) {
g_serial = cur_serial; g_property_serial = cur_serial;
char value[PROP_VALUE_MAX]; char value[PROP_VALUE_MAX];
__system_property_read(g_pinfo, 0, value); __system_property_read(g_pinfo, 0, value);
g_tags = strtoull(value, NULL, 0); g_tags = strtoull(value, nullptr, 0);
} }
result = ((g_tags & ATRACE_TAG_BIONIC) != 0); result = ((g_tags & ATRACE_TAG_BIONIC) != 0);
} }