strace java applet | 易学教程

问题

I'm trying to strace a java applet, and strace doesn't seem to be working. I'm calling the following function.

public static void testSTrace(){
    long c = 0;
    for (int i = 0; i < 1000; i++){
        long start = System.nanoTime();

        try{Thread.sleep(0, 100);}catch(Exception e){/*cry*/}

        long stop = System.nanoTime();

        log.info("start : " +start+" stop : "+stop);
    }
}

I get the following output from strace just before the above message is called and then nothing from strace:

clone(child_stack=0xb7c9f4c4,
flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|
CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID|CLONE_DETACHED,
parent_tidptr=0xb7c9fbf8, {entry_number:6, base_addr:0xb7c9fbb0,
limit:1048575, seg_32bit:1,
contents:0, read_exec_only:0,
limit_in_pages:1, seg_not_present:0, useable:1}, child_tidptr=0xb7c9fbf8) = 8351 futex(0xb7c9fbf8, FUTEX_WAIT, 8351, NULL

Once I start getting log output from the method, I get nothing more from strace. I'm pretty new to strace. Any clues on what is going on? Can applets be straced?

回答1:

You're probably only strace'ing a single thread. run strace with the -f flag.

回答2:

Three cheers for man pages, I want the follow forks flag, -f and -F

-f -- follow forks, -ff -- with output into separate files
-F -- attempt to follow vforks, -h -- print help message

strace -fF /bin/appletviewer test.html

now I get:

[pid  8401] gettimeofday({1248700317, 550296}, NULL) = 0
[pid  8401] gettimeofday({1248700317, 550401}, NULL) = 0
[pid  8401] gettimeofday({1248700317, 550500}, NULL) = 0
[pid  8401] gettimeofday({1248700317, 550626}, NULL) = 0
[pid  8401] gettimeofday({1248700317, 550883}, NULL) = 0
[pid  8401] gettimeofday({1248700317, 550993}, NULL) = 0
[pid  8401] gettimeofday({1248700317, 551093}, NULL) = 0

来源：https://stackoverflow.com/questions/1188075/strace-java-applet

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java

strace

nanotime