Piotr, On Friday 22 November 2013 09.21.56 Piotr Bzdyl wrote: > Is there any other information I could collect to help troubleshoot this > problem? How could I check if VM runs with attach disabled?
The comments in http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/tip/src/solaris/classes/sun/tools/attach/LinuxVirtualMachine.java describe the handshaking involved in dynamically enabling the attach mechanism on Linux. The mechanism is basically: * The attacher checks for the existence of the socket file /tmp/.java_pid${PID} * If that does not exist it creates a file .attach_pid${PID} in the target process' working directory and sends a SIGQUIT (kill -QUIT) to that process. * The SIGQUIT handler notices the .attach_pid${PID} file and creates the socket at /tmp/.java_pid${PID} * The attacher notices the socket file and unlinks the .attach_pid${PID} file. You can force the target process to always create the socket file at startup by using the -XX:+StartAttachListener command line flag. To further troubleshoot the problem I suggest that you try strace:ing the target process and jstack with the following flags enabled: (target process) $ strace -f -e trace=accept,stat,socket,bind $JAVA_HOME/bin/java donothing (jstack process) $ strace -f -e trace=open,connect,stat,unlink,write,kill $JAVA_HOME/bin/jstack <pid> You should get something similar to the following: (target process) (...) [pid 12602] --- SIGQUIT {si_signo=SIGQUIT, si_code=SI_USER, si_pid=12687, si_uid=726} --- [pid 12630] stat(".attach_pid12602", {st_mode=S_IFREG|0644, st_size=0, ...}) = 0 Process 12733 attached [pid 12733] socket(PF_LOCAL, SOCK_STREAM, 0) = 5 [pid 12733] bind(5, {sa_family=AF_LOCAL, sun_path="/tmp/.java_pid12602.tmp"}, 110) = 0 [pid 12733] accept(5, {sa_family=AF_LOCAL, NULL}, [2]) = 6 (jstack process) [pid 12688] stat("/localhome/java/jdk-8-ea-bin- b112/jre/lib/amd64/libattach.so", {st_mode=S_IFREG|0755, st_size=16029, ...}) = 0 [pid 12688] open("/localhome/java/jdk-8-ea-bin- b112/jre/lib/amd64/libattach.so", O_RDONLY) = 7 [pid 12688] open("/localhome/java/jdk-8-ea-bin- b112/jre/lib/amd64/libattach.so", O_RDONLY|O_CLOEXEC) = 7 [pid 12688] stat("/tmp/.java_pid12602", 0x7fe53183e3a0) = -1 ENOENT (No such file or directory) [pid 12688] open("/proc/12602/cwd/.attach_pid12602", O_RDWR|O_CREAT|O_EXCL, 0666) = 7 [pid 12688] kill(12602, SIGQUIT) = 0 [pid 12688] stat("/tmp/.java_pid12602", {st_mode=S_IFSOCK|0600, st_size=0, ...}) = 0 [pid 12688] unlink("/proc/12602/cwd/.attach_pid12602") = 0 [pid 12688] stat("/tmp/.java_pid12602", {st_mode=S_IFSOCK|0600, st_size=0, ...}) = 0 [pid 12688] connect(7, {sa_family=AF_LOCAL, sun_path="/tmp/.java_pid12602"}, 110) = 0 [pid 12688] connect(7, {sa_family=AF_LOCAL, sun_path="/tmp/.java_pid12602"}, 110) = 0 [pid 12688] write(7, "1", 1) = 1 [pid 12688] write(7, "\0", 1) = 1 [pid 12688] write(7, "threaddump", 10) = 10 [pid 12688] write(7, "\0", 1) = 1 /Mikael > > I noticed the same behavior when trying to connect to the process using > JConsole: JConsole displays the sample app in the list and when I try to > connect it finally displays an error that it cannot connect whereas the > sample app prints thread dump on its console. > > On Thu, Nov 21, 2013 at 7:18 PM, Alan Bateman <alan.bate...@oracle.com>wrote: > > On 21/11/2013 14:47, David Holmes wrote: > >> I can recreate this using the minimal VM, which doesn't support > >> libattach. So it definitely seems like something is going wrong in the > >> attach process, but I can't say what. Not sure what debugging hooks we > >> have > >> for the attach mechanism ?? > > > > The first attach involves signaling the target VM to start up the attach > > mechanism. So for the minimal VM or a VM running with attach disabled (or > > as Staffan pointed out, running with a different tmp directory) then the > > target VM gets a SIGQUIT and just prints the thread dump. It's hard to say > > what Piotr is running into but I think this at least explains it for the > > minimal VM. > > > > -Alan
