On Mon, 10 Jan 2022 05:19:26 GMT, Xin Liu <x...@openjdk.org> wrote: > In early stage of initialization, HotSpot doesn't handle SIGQUIT. The default > signal preposition on Linux is to quit the process and generate coredump. > > There are 2 applications for this signal. > 1. There's a handshake protocol between sun.tools.attach and HotSpot. > VirtualMachineImpl sends SIGQUIT(3) if the AttachListener has not been > initialized. It expects "Signal Dispatcher" to handle SIGQUIT and create > AttachListener. > 2. POSIX systems use SIGQUIT as SIGBREAK. After AttachListener is up, HotSpot > will reinterpret the signal for thread dump. > > It is possible that HotSpot is still initializing in Threads::create_vm() > when SIGQUIT arrives. We should change JVM_HANDLE_XXX_SIGNAL to catch SIGQUIT > and ignore it. It is installed os::init_2() and should cover the early stage > of initialization. Later on, os::initialize_jdk_signal_support() still > overwrites the signal handler of SIGQUIT if ReduceSignalUsage is > false(default). > > Testing > > Before, this patch, once initialization takes long time, jcmd may quit the > java process. > > $java -Xms64g -XX:+AlwaysPreTouch -Xlog:gc+heap=debug:stderr > -XX:ParallelGCThreads=1 & > [1] 9589 > [0.028s][debug][gc,heap] Minimum heap 68719476736 Initial heap 68719476736 > Maximum heap 68719476736 > [0.034s][debug][gc,heap] Running G1 PreTouch with 1 workers for 16384 work > units pre-touching 68719476736B. > $jcmd 9589 VM.flags > 9589: > [1] + 9589 quit java -Xms64g -XX:+AlwaysPreTouch > -Xlog:gc+heap=debug:stderr > java.io.IOException: No such process > at jdk.attach/sun.tools.attach.VirtualMachineImpl.sendQuitTo(Native > Method) > at > jdk.attach/sun.tools.attach.VirtualMachineImpl.<init>(VirtualMachineImpl.java:100) > at > jdk.attach/sun.tools.attach.AttachProviderImpl.attachVirtualMachine(AttachProviderImpl.java:58) > at > jdk.attach/com.sun.tools.attach.VirtualMachine.attach(VirtualMachine.java:207) > at jdk.jcmd/sun.tools.jcmd.JCmd.executeCommandForPid(JCmd.java:113) > at jdk.jcmd/sun.tools.jcmd.JCmd.main(JCmd.java:97) > > > With this patch, neither jcmd nor kill -3 will disrupt java process 45850. > > $java -Xms64g -XX:+AlwaysPreTouch -XX:ParallelGCThreads=1 -version & > [1] 45850 > $ kill -3 45850 > $jcmd 45850 VM.flags > 45850: > com.sun.tools.attach.AttachNotSupportedException: Unable to open socket file > /proc/45850/root/tmp/.java_pid45850: target process 45850 doesn't respond > within 10500ms or HotSpot VM not loaded > at > jdk.attach/sun.tools.attach.VirtualMachineImpl.<init>(VirtualMachineImpl.java:105) > at > jdk.attach/sun.tools.attach.AttachProviderImpl.attachVirtualMachine(AttachProviderImpl.java:58) > at > jdk.attach/com.sun.tools.attach.VirtualMachine.attach(VirtualMachine.java:207) > at jdk.jcmd/sun.tools.jcmd.JCmd.executeCommandForPid(JCmd.java:113) > at jdk.jcmd/sun.tools.jcmd.JCmd.main(JCmd.java:97) > $openjdk version "19-internal" 2022-09-20 > OpenJDK Runtime Environment (fastdebug build 19-internal+0-adhoc.xxinliu.jdk) > OpenJDK 64-Bit Server VM (fastdebug build 19-internal+0-adhoc.xxinliu.jdk, > mixed mode, sharing) > [1] + 45850 done java -Xms64g -XX:+AlwaysPreTouch > -XX:ParallelGCThreads=1 -version
This pull request has now been integrated. Changeset: 9bf6ffa1 Author: Xin Liu <x...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/9bf6ffa19f1ea9efcadb3396d921305c9ec0b1d1 Stats: 14 lines in 1 file changed: 10 ins; 0 del; 4 mod 8279124: VM does not handle SIGQUIT during initialization Reviewed-by: dholmes, stuefe ------------- PR: https://git.openjdk.java.net/jdk/pull/7003
