(Void&&) ()
#23 0x0000000001eeb81e in N2::Net2::run() ()
#24 0x0000000000783a8f in main ()
```
As we can see, handling c++ exceptions is interrupted by a signal. The `profileHandler` indicates this signal is SIGPROF raised by Profiler Thread. Handling exceptions and handling signals are both locking the same non-reentrant mutex in `_Unwind_Find_FDE` when unwinding stacktrace. So fdbserver encounters a deadlock.
My questions are:
(1) Now I do not setup profiler thread to avoid this case. Is there any other potential problem if I close Profiler Thread?
(2) In foundationdb 7.x, there is a better `backtrace` implemented by `absl::GetStackTrace`. While in `profileHandler`, the original `backtrace` is invoked and we may also encounter this deadlock. So is there any plan to fix this invocation? And is there any possibility to make this better `backtrace` implementation backport to foundationdb 6.x?
---
### Author:  [@jzhou](https://forums.foundationdb.org/u/jzhou)
#### Post date: [April 23, 2023, 12:10am UTC](https://forums.foundationdb.org/t/deadlock-caused-by-profiler-thread-in-storage-server/3921/2 "2023-04-23T00:10:27Z")
Good catch! Looks like `profileHandler` should switch to use the same `absl::GetStackTrace` if available.
---
### Author:  [@ajbeamon](https://forums.foundationdb.org/u/ajbeamon)
#### Post date: [April 23, 2023, 10:54pm UTC](https://forums.foundationdb.org/t/deadlock-caused-by-profiler-thread-in-storage-server/3921/3 "2023-04-23T22:54:05Z")
Were you by any chance using a sanitizer? There is a workaround to this problem employed by FDB, but it does not work in sanitizers. There may be other builds that it doesn’t work in either.
The absl stack trace has other problems that made it not work in this use case. The source is those issues hasn’t been discovered yet, and until then the existing backtrace works better in practice.
---
### Author:  [@atn34](https://forums.foundationdb.org/u/atn34)
#### Post date: [April 24, 2023, 5:24pm UTC](https://forums.foundationdb.org/t/deadlock-caused-by-profiler-thread-in-storage-server/3921/4 "2023-04-24T17:24:21Z")
Something I just noticed while revisiting this is that [this line](https://github.com/apple/foundationdb/blob/bcc89944f0da07749c9df01d8081d99cc200d47d/flow/Profiler.actor.cpp#L193) originally referred to calling the libc `backtrace` implementation, but now it’s calling the absl implementation, which presumably does not have the originally-intended effect.
> [@GestureWei](#):
>
> (1) Now I do not setup profiler thread to avoid this case. Is there any other potential problem if I close Profiler Thread?
This shouldn’t be a problem. The slow task profiler is a diagnostic tool to help identify certain performance problems, and isn’t necessary for normal operation.
I agree with AJ - 6.3.25 is believed to have this problem mitigated (except in sanitizer builds). Can you share a bit more about whether or not you built from source or downloaded an official binary, and what environment you’re running in? Maybe what libc implementation?
---
### Author:  [@GestureWei](https://forums.foundationdb.org/u/GestureWei)
#### Post date: [April 25, 2023, 2:43am UTC](https://forums.foundationdb.org/t/deadlock-caused-by-profiler-thread-in-storage-server/3921/5 "2023-04-25T02:43:26Z")
> This shouldn’t be a problem. The slow task profiler is a diagnostic tool to help identify certain performance problems, and isn’t necessary for normal operation.
Thanks a lot for this reply. When I close profiler, the problem seems to be disappeared.
There is something more I could share. I built FDB from source without sanitizers. The building and running environment is:
```auto
OS: CentOS 7
Compiler: gcc 8.3.1 in devtoolset-8
Glibc version: 2.17
Build type: RelWithDebInfo
```
I have learned about glibc-2.17 source and then find `backtrace` in libgcc may encounter deadlock when using AddressSanitizer. But my deadlock case is not caused by sanitizer. So is there any other ideas about this case? Or is there any other information I can provide?
---
### Author:  [@GestureWei](https://forums.foundationdb.org/u/GestureWei)
#### Post date: [April 25, 2023, 2:44am UTC](https://forums.foundationdb.org/t/deadlock-caused-by-profiler-thread-in-storage-server/3921/6 "2023-04-25T02:44:09Z")
No. I built FDB without sanitizers.
---
### Author:  [@GestureWei](https://forums.foundationdb.org/u/GestureWei)
#### Post date: [April 25, 2023, 2:52am UTC](https://forums.foundationdb.org/t/deadlock-caused-by-profiler-thread-in-storage-server/3921/7 "2023-04-25T02:52:48Z")
Thanks for your reply.
Closing profiler seems to be a solution to this case now, but I think throwing this issues in forum and trying to find a solution can help to make FDB better.