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Improve observer that logs blocked threads.

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This commit is contained in:
Greyson Parrelli 2021-10-13 11:00:48 -04:00
parent 7866e2e29c
commit 168481fee5
1 changed files with 29 additions and 7 deletions
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36
core-util/src/main/java/org/signal/core/util/concurrent/DeadlockDetector.kt
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@ -1,9 +1,7 @@
package org.signal.core.util.concurrent package org.signal.core.util.concurrent
import android.os.Handler import android.os.Handler
import android.os.SystemClock
import org.signal.core.util.logging.Log import org.signal.core.util.logging.Log
import java.util.concurrent.TimeUnit
/** /**
* A class that polls active threads at a set interval and logs when multiple threads are BLOCKED. * A class that polls active threads at a set interval and logs when multiple threads are BLOCKED.
@ -11,6 +9,7 @@ import java.util.concurrent.TimeUnit
class DeadlockDetector(private val handler: Handler, private val pollingInterval: Long) { class DeadlockDetector(private val handler: Handler, private val pollingInterval: Long) {
private var running = false private var running = false
private val previouslyBlocked: MutableSet<Long> = mutableSetOf()
fun start() { fun start() {
Log.d(TAG, "Beginning deadlock monitoring."); Log.d(TAG, "Beginning deadlock monitoring.");
@ -25,13 +24,36 @@ class DeadlockDetector(private val handler: Handler, private val pollingInterval
} }
private fun poll() { private fun poll() {
val threads = Thread.getAllStackTraces() val threads: Map<Thread, Array<StackTraceElement>> = Thread.getAllStackTraces()
val blocked = threads.filterKeys { thread -> thread.state == Thread.State.BLOCKED } val blocked: Map<Thread, Array<StackTraceElement>> = threads.filter { entry ->
val thread: Thread = entry.key
val stack: Array<StackTraceElement> = entry.value
thread.state == Thread.State.BLOCKED || (thread.state == Thread.State.WAITING && stack.any { it.methodName.startsWith("lock") })
}
val blockedIds: Set<Long> = blocked.keys.map(Thread::getId).toSet()
if (blocked.size > 1) { if (blocked.size > 1) {
Log.w(TAG, buildLogString(blocked)) Log.w(TAG, buildLogString("Found multiple blocked threads! Possible deadlock.", blocked))
} else {
val stillBlocked: Set<Long> = blockedIds.intersect(previouslyBlocked)
if (stillBlocked.isNotEmpty()) {
val stillBlockedMap: Map<Thread, Array<StackTraceElement>> = stillBlocked
.map { blockedId ->
val key: Thread = blocked.keys.first { it.id == blockedId }
val value: Array<StackTraceElement> = blocked[key]!!
Pair(key, value)
}
.toMap()
Log.w(TAG, buildLogString("Found a long block! Blocked for at least $pollingInterval ms.", stillBlockedMap))
}
} }
previouslyBlocked.clear()
previouslyBlocked.addAll(blockedIds)
if (running) { if (running) {
handler.postDelayed(this::poll, pollingInterval) handler.postDelayed(this::poll, pollingInterval)
} }
@ -40,9 +62,9 @@ class DeadlockDetector(private val handler: Handler, private val pollingInterval
companion object { companion object {
private val TAG = Log.tag(DeadlockDetector::class.java) private val TAG = Log.tag(DeadlockDetector::class.java)
private fun buildLogString(blocked: Map<Thread, Array<StackTraceElement>>): String { private fun buildLogString(description: String, blocked: Map<Thread, Array<StackTraceElement>>): String {
val stringBuilder = StringBuilder() val stringBuilder = StringBuilder()
stringBuilder.append("Found multiple blocked threads! Possible deadlock.\n") stringBuilder.append(description).append("\n")
for (entry in blocked) { for (entry in blocked) {
stringBuilder.append("-- [${entry.key.id}] ${entry.key.name}\n") stringBuilder.append("-- [${entry.key.id}] ${entry.key.name}\n")