logd: reader/writer element locks
Switch to a reader writer lock for the Element List lock. Also setup
for a reader writer lock for the Times list, but continue to use a
mutex where rdlock() and wrlock() are the same implementation for now.
This should improve general reader performance and prevent blocking of
other reader operations or exit by a single hung logd.reader.per
thread. For example, a full length logcat of an empty buffer (eg:
crash log buffer) will hold a lock while the iterator scans the entire
list.
Test: gTest liblog-unit-tests, logd-unit-tests, logcat-unit-tests
Bug: 37378309
Bug: 37483775
Change-Id: If5723ff4a978e17d828a75321e8f0ba91d4a09e0
diff --git a/logd/LogBuffer.cpp b/logd/LogBuffer.cpp
index ed46181..d9ec081 100644
--- a/logd/LogBuffer.cpp
+++ b/logd/LogBuffer.cpp
@@ -72,7 +72,7 @@
// as the act of mounting /data would trigger persist.logd.timestamp to
// be corrected. 1/30 corner case YMMV.
//
- pthread_mutex_lock(&mLogElementsLock);
+ rdlock();
LogBufferElementCollection::iterator it = mLogElements.begin();
while ((it != mLogElements.end())) {
LogBufferElement* e = *it;
@@ -87,7 +87,7 @@
}
++it;
}
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
}
// We may have been triggered by a SIGHUP. Release any sleeping reader
@@ -95,7 +95,7 @@
//
// NB: this is _not_ performed in the context of a SIGHUP, it is
// performed during startup, and in context of reinit administrative thread
- LogTimeEntry::lock();
+ LogTimeEntry::wrlock();
LastLogTimes::iterator times = mTimes.begin();
while (times != mTimes.end()) {
@@ -111,7 +111,7 @@
LogBuffer::LogBuffer(LastLogTimes* times)
: monotonic(android_log_clockid() == CLOCK_MONOTONIC), mTimes(*times) {
- pthread_mutex_init(&mLogElementsLock, nullptr);
+ pthread_rwlock_init(&mLogElementsLock, nullptr);
log_id_for_each(i) {
lastLoggedElements[i] = nullptr;
@@ -207,15 +207,15 @@
}
if (!__android_log_is_loggable(prio, tag, ANDROID_LOG_VERBOSE)) {
// Log traffic received to total
- pthread_mutex_lock(&mLogElementsLock);
+ wrlock();
stats.addTotal(elem);
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
delete elem;
return -EACCES;
}
}
- pthread_mutex_lock(&mLogElementsLock);
+ wrlock();
LogBufferElement* currentLast = lastLoggedElements[log_id];
if (currentLast) {
LogBufferElement* dropped = droppedElements[log_id];
@@ -316,14 +316,14 @@
// check for overflow
if (total >= UINT32_MAX) {
log(currentLast);
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
return len;
}
stats.addTotal(currentLast);
delete currentLast;
swab = total;
event->payload.data = htole32(swab);
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
return len;
}
if (count == USHRT_MAX) {
@@ -340,7 +340,7 @@
}
droppedElements[log_id] = currentLast;
lastLoggedElements[log_id] = elem;
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
return len;
}
if (dropped) { // State 1 or 2
@@ -358,12 +358,12 @@
lastLoggedElements[log_id] = new LogBufferElement(*elem);
log(elem);
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
return len;
}
-// assumes mLogElementsLock held, owns elem, will look after garbage collection
+// assumes LogBuffer::wrlock() held, owns elem, look after garbage collection
void LogBuffer::log(LogBufferElement* elem) {
// cap on how far back we will sort in-place, otherwise append
static uint32_t too_far_back = 5; // five seconds
@@ -384,7 +384,7 @@
bool end_set = false;
bool end_always = false;
- LogTimeEntry::lock();
+ LogTimeEntry::rdlock();
LastLogTimes::iterator times = mTimes.begin();
while (times != mTimes.end()) {
@@ -426,7 +426,7 @@
// Prune at most 10% of the log entries or maxPrune, whichever is less.
//
-// mLogElementsLock must be held when this function is called.
+// LogBuffer::wrlock() must be held when this function is called.
void LogBuffer::maybePrune(log_id_t id) {
size_t sizes = stats.sizes(id);
unsigned long maxSize = log_buffer_size(id);
@@ -650,14 +650,14 @@
// The third thread is optional, and only gets hit if there was a whitelist
// and more needs to be pruned against the backstop of the region lock.
//
-// mLogElementsLock must be held when this function is called.
+// LogBuffer::wrlock() must be held when this function is called.
//
bool LogBuffer::prune(log_id_t id, unsigned long pruneRows, uid_t caller_uid) {
LogTimeEntry* oldest = nullptr;
bool busy = false;
bool clearAll = pruneRows == ULONG_MAX;
- LogTimeEntry::lock();
+ LogTimeEntry::rdlock();
// Region locked?
LastLogTimes::iterator times = mTimes.begin();
@@ -1017,15 +1017,15 @@
// one entry, not another clear run, so we are looking for
// the quick side effect of the return value to tell us if
// we have a _blocked_ reader.
- pthread_mutex_lock(&mLogElementsLock);
+ wrlock();
busy = prune(id, 1, uid);
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
// It is still busy, blocked reader(s), lets kill them all!
// otherwise, lets be a good citizen and preserve the slow
// readers and let the clear run (below) deal with determining
// if we are still blocked and return an error code to caller.
if (busy) {
- LogTimeEntry::lock();
+ LogTimeEntry::wrlock();
LastLogTimes::iterator times = mTimes.begin();
while (times != mTimes.end()) {
LogTimeEntry* entry = (*times);
@@ -1038,9 +1038,9 @@
LogTimeEntry::unlock();
}
}
- pthread_mutex_lock(&mLogElementsLock);
+ wrlock();
busy = prune(id, ULONG_MAX, uid);
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
if (!busy || !--retry) {
break;
}
@@ -1051,9 +1051,9 @@
// get the used space associated with "id".
unsigned long LogBuffer::getSizeUsed(log_id_t id) {
- pthread_mutex_lock(&mLogElementsLock);
+ rdlock();
size_t retval = stats.sizes(id);
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
return retval;
}
@@ -1063,17 +1063,17 @@
if (!__android_logger_valid_buffer_size(size)) {
return -1;
}
- pthread_mutex_lock(&mLogElementsLock);
+ wrlock();
log_buffer_size(id) = size;
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
return 0;
}
// get the total space allocated to "id"
unsigned long LogBuffer::getSize(log_id_t id) {
- pthread_mutex_lock(&mLogElementsLock);
+ rdlock();
size_t retval = log_buffer_size(id);
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
return retval;
}
@@ -1085,7 +1085,7 @@
LogBufferElementCollection::iterator it;
uid_t uid = reader->getUid();
- pthread_mutex_lock(&mLogElementsLock);
+ rdlock();
if (start == log_time::EPOCH) {
// client wants to start from the beginning
@@ -1143,7 +1143,7 @@
continue;
}
- // NB: calling out to another object with mLogElementsLock held (safe)
+ // NB: calling out to another object with wrlock() held (safe)
if (filter) {
int ret = (*filter)(element, arg);
if (ret == false) {
@@ -1166,7 +1166,7 @@
(element->getDropped() && !sameTid) ? 0 : element->getTid();
}
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
// range locking in LastLogTimes looks after us
max = element->flushTo(reader, this, privileged, sameTid);
@@ -1176,20 +1176,20 @@
}
skip = maxSkip;
- pthread_mutex_lock(&mLogElementsLock);
+ rdlock();
}
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
return max;
}
std::string LogBuffer::formatStatistics(uid_t uid, pid_t pid,
unsigned int logMask) {
- pthread_mutex_lock(&mLogElementsLock);
+ wrlock();
std::string ret = stats.format(uid, pid, logMask);
- pthread_mutex_unlock(&mLogElementsLock);
+ unlock();
return ret;
}