logd: clear return and deal with busy if readers locked
- Propagate to caller the clearing errors, busy blocked by reader.
- For clear, perform retries within logd with a one second lul each,
telling readers to skip, but on final retry to kill all readers if
problem still persists due to block reader (or high volume logspammer).
Bug: 23711431
Change-Id: Ie4c46bc9480a7f49b96a81fae25a95c603270c33
diff --git a/logd/CommandListener.cpp b/logd/CommandListener.cpp
index 031c740..eafa28f 100644
--- a/logd/CommandListener.cpp
+++ b/logd/CommandListener.cpp
@@ -96,8 +96,7 @@
return 0;
}
- mBuf.clear((log_id_t) id, uid);
- cli->sendMsg("success");
+ cli->sendMsg(mBuf.clear((log_id_t) id, uid) ? "busy" : "success");
return 0;
}
diff --git a/logd/LogBuffer.cpp b/logd/LogBuffer.cpp
index c2f846e..35ee6f3 100644
--- a/logd/LogBuffer.cpp
+++ b/logd/LogBuffer.cpp
@@ -374,8 +374,9 @@
//
// mLogElementsLock must be held when this function is called.
//
-void LogBuffer::prune(log_id_t id, unsigned long pruneRows, uid_t caller_uid) {
+bool LogBuffer::prune(log_id_t id, unsigned long pruneRows, uid_t caller_uid) {
LogTimeEntry *oldest = NULL;
+ bool busy = false;
LogTimeEntry::lock();
@@ -397,6 +398,8 @@
LogBufferElement *e = *it;
if (oldest && (oldest->mStart <= e->getSequence())) {
+ oldest->triggerSkip_Locked(id, pruneRows);
+ busy = true;
break;
}
@@ -416,7 +419,7 @@
}
}
LogTimeEntry::unlock();
- return;
+ return busy;
}
// prune by worst offender by uid
@@ -478,6 +481,7 @@
LogBufferElement *e = *it;
if (oldest && (oldest->mStart <= e->getSequence())) {
+ busy = true;
break;
}
@@ -596,6 +600,8 @@
}
if (oldest && (oldest->mStart <= e->getSequence())) {
+ busy = true;
+
if (whitelist) {
break;
}
@@ -631,6 +637,7 @@
}
if (oldest && (oldest->mStart <= e->getSequence())) {
+ busy = true;
if (stats.sizes(id) > (2 * log_buffer_size(id))) {
// kick a misbehaving log reader client off the island
oldest->release_Locked();
@@ -646,13 +653,50 @@
}
LogTimeEntry::unlock();
+
+ return (pruneRows > 0) && busy;
}
// clear all rows of type "id" from the buffer.
-void LogBuffer::clear(log_id_t id, uid_t uid) {
- pthread_mutex_lock(&mLogElementsLock);
- prune(id, ULONG_MAX, uid);
- pthread_mutex_unlock(&mLogElementsLock);
+bool LogBuffer::clear(log_id_t id, uid_t uid) {
+ bool busy = true;
+ // If it takes more than 4 tries (seconds) to clear, then kill reader(s)
+ for (int retry = 4;;) {
+ if (retry == 1) { // last pass
+ // Check if it is still busy after the sleep, we say prune
+ // 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);
+ busy = prune(id, 1, uid);
+ pthread_mutex_unlock(&mLogElementsLock);
+ // 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();
+ LastLogTimes::iterator times = mTimes.begin();
+ while (times != mTimes.end()) {
+ LogTimeEntry *entry = (*times);
+ // Killer punch
+ if (entry->owned_Locked() && entry->isWatching(id)) {
+ entry->release_Locked();
+ }
+ times++;
+ }
+ LogTimeEntry::unlock();
+ }
+ }
+ pthread_mutex_lock(&mLogElementsLock);
+ busy = prune(id, ULONG_MAX, uid);
+ pthread_mutex_unlock(&mLogElementsLock);
+ if (!busy || !--retry) {
+ break;
+ }
+ sleep (1); // Let reader(s) catch up after notification
+ }
+ return busy;
}
// get the used space associated with "id".
diff --git a/logd/LogBuffer.h b/logd/LogBuffer.h
index de76693..d8e0b90 100644
--- a/logd/LogBuffer.h
+++ b/logd/LogBuffer.h
@@ -63,7 +63,7 @@
int (*filter)(const LogBufferElement *element, void *arg) = NULL,
void *arg = NULL);
- void clear(log_id_t id, uid_t uid = AID_ROOT);
+ bool clear(log_id_t id, uid_t uid = AID_ROOT);
unsigned long getSize(log_id_t id);
int setSize(log_id_t id, unsigned long size);
unsigned long getSizeUsed(log_id_t id);
@@ -86,7 +86,7 @@
private:
void maybePrune(log_id_t id);
- void prune(log_id_t id, unsigned long pruneRows, uid_t uid = AID_ROOT);
+ bool prune(log_id_t id, unsigned long pruneRows, uid_t uid = AID_ROOT);
LogBufferElementCollection::iterator erase(
LogBufferElementCollection::iterator it, bool engageStats = true);
};
