Avoid polling when detecting ANRs by invoking JNI from SIGQUIT handler #741
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bugsnag-plugin-android-anr/src/main/java/com/bugsnag/android/AnrInterface.java
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Apologies - it seems as those an old stale artefact must have been lying around the system, which meant ANRs appeared to work fine in the example app. I've altered |
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bugsnag-plugin-android-anr/src/main/java/com/bugsnag/android/AnrPlugin.kt
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The previous implementation of ANR detection used a SIGQUIT handler. When SIGQUIT was raised, a shared ByteBuffer was modified, and the JVM layer polled every 5ms to check whether an ANR had occurred. Polling every 5ms is inefficient and risks an app being killed if it is in the background due to excessive work. This alternative approach invokes the JNI from the SIGQUIT handler and avoids the need for polling entirely.
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Goal
The previous implementation of ANR detection used a SIGQUIT handler. When SIGQUIT was raised, a shared ByteBuffer was modified, and the JVM layer polled every 5ms to check whether an ANR had occurred.
Polling every 5ms is inefficient and risks an app being killed if it is in the background due to excessive work. This alternative approach invokes the JNI from the SIGQUIT handler and avoids the need for polling entirely.
Changeset
AnrInterfaceclass which is responsible for all communication from the ANR layer to the JVM layerAnrPlugininitialisation so that aByteBufferis no longer requiredcollectAnrErrorDetails()accessible fromAnrInterface(the containing class is still non-public)AppNotRespondingMonitorclassANR handler
AnrInterfaceinJni_On_Load, as JNIEnv is not thread safe and we need to obtain a reference each time the ANR handler is invokedSA_ONSTACKflag from SIGQUIT handler installation as we don't require information about the signal; we just need to know that it happenedAnrInterfacethrough JNI in the SIGQUIT handlerTests
I have verified that ANRs are detected on the following devices, and that changing
releaseStagealters whether the error is detected or not: