deadlock on app relaunch (triggered by device rotation)

[0x53A]

I need to preface this with that I'm not sure if the bug is here, in winit, or in my own app.

I have a small toy android application which uses egui, winit, android-activity: https://github.com/0x53A/UAS-SigVer

The app works fine when launched in either horizontal or vertical, but crashes when rotated.

Looking through the ANR report, there seems to be a deadlock, triggered by app relaunch. It's not fully clear to me why rotation triggers a relaunch anyway, because the template I'm using (https://github.com/tauri-apps/cargo-mobile2) already defines <activity android:configChanges="orientation|keyboardHidden", but the relaunch can be averted by adding screenSize|screenLayout (https://github.com/tauri-apps/cargo-mobile2/pull/458/files).

Averting the relaunch fixes rotation, but I don't think the app should deadlock on relaunch anyway, so it just hides the symptom.

Here is an excerpt of the two callstacks, the full log is here: 0x53A/UAS-SigVer#1

----- pid 22451 at 2025-05-06 00:42:55.372396957+0200 -----
Cmd line: com.x53a.uas_sigver
Build fingerprint: 'Xiaomi/pyxis_eea/pyxis:11/RKQ1.200826.002/V12.5.3.0.RFCEUXM:user/release-keys'
ABI: 'arm64'
Build type: optimized
Debug Store: 1,0,1037607671::
suspend all histogram:	Sum: 167us 99% C.I. 7us-29us Avg: 12.846us Max: 29us
DALVIK THREADS (19):
"main" prio=5 tid=1 Native
  | group="main" sCount=1 ucsCount=0 flags=1 obj=0x72bc8828 self=0x6efde12380
  | sysTid=22451 nice=-10 cgrp=default sched=0/0 handle=0x6fdce980a0
  | state=S schedstat=( 590665321 91558550 1111 ) utm=44 stm=15 core=5 HZ=100
  | stack=0x7ff294b000-0x7ff294d000 stackSize=8188KB
  | held mutexes=
  native: #00 pc 0007ff4c  /apex/com.android.runtime/lib64/bionic/libc.so (syscall+28) (BuildId: d2b63e277d4fb6976635d39171f71be5)
  native: #01 pc 01447920  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (std::sys::sync::condvar::futex::Condvar::wait::h36588761a73d12e9+112)
  native: #02 pc 01192810  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (std::sync::poison::condvar::Condvar::wait::h1d01febd47439c66+48)
  native: #03 pc 01152e50  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (android_activity::activity_impl::glue::WaitableNativeActivityState::notify_destroyed::ha32a1b9aac6b6587+452)
  native: #04 pc 0115915c  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (android_activity::activity_impl::glue::on_destroy::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h25efd2a0740ef5be+64)
  native: #05 pc 01157a3c  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (android_activity::activity_impl::glue::try_with_waitable_activity_ref::h9e2515851c93973a+432)
  native: #06 pc 0115906c  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (android_activity::activity_impl::glue::on_destroy::_$u7b$$u7b$closure$u7d$$u7d$::hb6e9a71da5ea1f27+52)
  native: #07 pc 01195064  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (_$LT$core..panic..unwind_safe..AssertUnwindSafe$LT$F$GT$$u20$as$u20$core..ops..function..FnOnce$LT$$LP$$RP$$GT$$GT$::call_once::h674bec53079afde7+16)
  native: #08 pc 011962f8  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (std::panicking::try::do_call::hc8575558740f866c+40)
  native: #09 pc 01192748  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (__rust_try+24)
  native: #10 pc 0118ff38  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (std::panic::catch_unwind::he548fcda22bded20+48)
  native: #11 pc 01189c54  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (android_activity::util::abort_on_panic::hec9cd527a0ed0245+16)
  native: #12 pc 01159020  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (android_activity::activity_impl::glue::on_destroy::h0a7a714bc732c254+20)
  native: #13 pc 0010467c  /system/lib64/libandroid_runtime.so (android::NativeCode::~NativeCode+48) (BuildId: 2322557e6de9bc2935568e245609a468)
  native: #14 pc 00103ef4  /system/lib64/libandroid_runtime.so (android::unloadNativeCode_native+24) (BuildId: 2322557e6de9bc2935568e245609a468)
[...]
  at android.app.NativeActivity.onDestroy(NativeActivity.java:198)
[...]
  at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:6276)
  at android.app.servertransaction.ActivityRelaunchItem.execute(ActivityRelaunchItem.java:106)
[...]

"Thread-2" prio=10 tid=15 Native
  | group="main" sCount=1 ucsCount=0 flags=1 obj=0x14440678 self=0x6efde481b0
  | sysTid=22474 nice=-10 cgrp=default sched=0/0 handle=0x6d190c3710
  | state=S schedstat=( 64171695081 113185684 5701 ) utm=6295 stm=122 core=6 HZ=100
  | stack=0x6d18ec4000-0x6d18ec6000 stackSize=2045KB
  | held mutexes=
  native: #00 pc 000bda28  /apex/com.android.runtime/lib64/bionic/libc.so (__epoll_pwait+8) (BuildId: d2b63e277d4fb6976635d39171f71be5)
  native: #01 pc 00015abc  /system/lib64/libutils.so (android::Looper::pollAll+232) (BuildId: 3b5fcb253cc00622c9fd2464adbd2aab)
  native: #02 pc 0001df0c  /system/lib64/libandroid.so (ALooper_pollAll+100) (BuildId: d4449b6b5251bcbb324253a7b1fd9eb3)
  native: #03 pc 005ca004  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (android_activity::activity_impl::AndroidAppInner::poll_events::ha523ccab9468a961+676)
  native: #04 pc 005d58e8  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (android_activity::AndroidApp::poll_events::hc8faa7d8c0c02863+376)
  native: #05 pc 007c1d64  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (winit::platform_impl::android::EventLoop$LT$T$GT$::poll_events_with_timeout::h369f8c0d4c866f48+532)
  native: #06 pc 007b7ed4  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (winit::platform_impl::android::EventLoop$LT$T$GT$::pump_events::habfba97826f35aae+204)
  native: #07 pc 007b8094  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (winit::platform_impl::android::EventLoop$LT$T$GT$::run_on_demand::h4cb195aea24d4477+56)
  native: #08 pc 007c23b4  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (winit::platform_impl::android::EventLoop$LT$T$GT$::run::hce9d1c3230e20d23+20)
  native: #09 pc 005dc830  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (winit::event_loop::EventLoop$LT$T$GT$::run_app::hd5c8e1a29b46e777+64)
  native: #10 pc 005ea0e0  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (uas_sigver::_main::h8bb3d57897411549+480)
  native: #11 pc 007b5dc0  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (uas_sigver::android_main::_$u7b$$u7b$closure$u7d$$u7d$::h415ad26d0a164df6+36)
  native: #12 pc 005d5678  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (_$LT$core..panic..unwind_safe..AssertUnwindSafe$LT$F$GT$$u20$as$u20$core..ops..function..FnOnce$LT$$LP$$RP$$GT$$GT$::call_once::hd1ddba994bca9ad9+36)
  native: #13 pc 0060f618  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (std::panicking::try::do_call::h73570f4f47564d80+60)
  native: #14 pc 00611e7c  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (__rust_try+24)
  native: #15 pc 00611d6c  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (std::panic::catch_unwind::h8c1c77e1ceb234e1+84)
  native: #16 pc 007b5cec  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (uas_sigver::stop_unwind::h596a23a5ce7b72e5+36)
  native: #17 pc 005ea3dc  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (android_main+460)
  native: #18 pc 0115b5a8  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (android_activity::activity_impl::glue::ANativeActivity_onCreate::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h5efa3872064905a9+16)
  native: #19 pc 01196400  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (std::panicking::try::do_call::he1f99e3e11bde350+40)
  native: #20 pc 01192748  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (__rust_try+24)
  native: #21 pc 0118f8d4  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (std::panic::catch_unwind::h7c50a2f319ed614a+48)
  native: #22 pc 0115b2b8  /data/app/~~X7jrRRNnLoEuyFBbocVUhQ==/com.x53a.uas_sigver-heXnhgzm_FjkVnMb3gTwTg==/base.apk (offset 8c82000) (android_activity::activity_impl::glue::ANativeActivity_onCreate::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h467dabaf06f3fed3+520)
[...]

I've created the issue here, because android-activity is at the top of the callstack in both threads (android_activity::activity_impl::AndroidAppInner::poll_events and android_activity::activity_impl::glue::WaitableNativeActivityState::notify_destroyed), but it could just as well be an issue with winit or something else, I haven't yet looked too deep into it.

[MarijnS95]

@0x53A this is unfortunately expected, because android-activity doesn't yet support handling the lifecycle of multiple Activitys. It always considers this instance a singleton even if it's not in most cases.

As you already found, adding screenSize|screenLayout is the desired workaround since you'll just get a callback/event to tell you about size changes (mostly width/height swapping) rather than fully restarting the Activity. That should be a bit smoother on your app in any case.

---

Since there are many more cases where handling multiple Activitys is absolutely required, I'm still working on refactoring/rewriting this crate to support that (and subsequent winit changes), but it's a long process that I can't always find the time to chip away on. Thanks for understanding! 🙏

EDIT: There should be multiple issues tracking this such as #58, I might close this as duplicate :)

[rib]

I'm re-opening this in order to differentiate this lifecycle dead lock (due to configuration changes that try to re-create the whole Activity) from #58 which has a much simpler explanation (ndk-context asserts that it does not get initialized more than once).

Assuming we can avoid the panic in ndk-context then android-activity itself doesn't have any static state and it's not obvious to me why it shouldn't be able to technically track the lifecycle of multiple Activities (even if NativeActivity is not really designed for that).

From the two backtraces it looks like the java main thread has been notified of the activity being destroyed and it's blocked waiting for the android_main thread to acknowledge this.

It's not immediately obvious why the guard.write_cmd(AppCmd::Destroy) hasn't woken up the other thread, which is currently just stuck polling for events.

If the Thread-2 android_main thread is a new android_main thread (spawned for the new Activity) that doesn't hold the other end message pipe then it's not obvious why there wouldn't have been an IO error when writing the Destroy command or why it didn't transition to NativeThreadState::Stopped before exiting.