Crash Dump Analysis Patterns (Part 187, Linux)

Here we publish a Linux variant of Active Thread pattern that was previously introduced for Mac OS X and Windows. Basically it is a thread that is not waiting, sleeping, or suspended (most threads are). However, from a memory dump it is not possible to find out whether it was Spiking Thread at the dump generation time (unless we have a set of memory snapshots and in each one we have the same or similar back trace) and we don’t have any Paratext with CPU consumption stats for threads. For example, in one core dump we have this thread:

(gdb) info threads
Id Target Id Frame
6 Thread 0×7f560d467700 (LWP 3483) 0×00000000004324a9 in clone ()
5 Thread 0×7f560c465700 (LWP 3485) 0×000000000042fe31 in nanosleep ()
4 Thread 0×7f560bc64700 (LWP 3486) 0×000000000042fe31 in nanosleep ()
3 Thread 0×7f560b463700 (LWP 3487) 0×000000000042fe31 in nanosleep ()
2 Thread 0×18b9860 (LWP 3482) 0×000000000042fe31 in nanosleep ()
1 Thread 0×7f560cc66700 (LWP 3484) 0×000000000042fe31 in nanosleep ()

Thread #6 is not waiting so we inspect its back trace:

(gdb) thread 6
[Switching to thread 6 (Thread 0x7f560d467700 (LWP 3483))]
#0 0x00000000004324a9 in clone ()

(gdb) bt
#0 0×00000000004324a9 in clone ()
#1 0×0000000000401560 in ?? () at pthread_create.c:217
#2 0×00007f560d467700 in ?? ()
#3 0×0000000000000000 in ?? ()

(gdb) x/i 0x4324a9
=> 0x4324a9 : test %rax,%rax

Perhaps the core dump was saved at the thread creation time.

- Dmitry Vostokov @ + -

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