1194180 - Nuwa: MOZ_ALWAYS_TRUE(NS_SUCCEEDED(NS_DispatchToMainThread(runnable)));

Status: RESOLVED WONTFIX

(Firefox OS Graveyard :: General, defect)

Description

[Gregor Wagner [:gwagner]]

Attachment: gdb bt

Seen on current trunk on aries with debug gecko and monkey testing.

Comment 1

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Can you get a backtrace for the main thread too?

Comment 2

[Gregor Wagner [:gwagner]]

Attachment: main thread

Comment 3

[Gregor Wagner [:gwagner]]

Hm thats interesting. 2 PA processes:
root@aries:/ # b2g-ps
APPLICATION    SEC USER     PID   PPID  VSIZE  RSS     WCHAN    PC         NAME
b2g              0 root      5131  1     340116 131532 ffffffff b6ea72d4 t /system/b2g/b2g
(Nuwa)           0 root      5138  5131  116028 26012 ffffffff b6ea6a60 S /system/b2g/b2g
Homescreen       2 u0_a5468  5468  5138  148500 51608 ffffffff b6ea6894 S /system/b2g/b2g
OperatorVariant  2 u0_a5498  5498  5138  131180 39240 ffffffff b6ea6894 S /system/b2g/b2g
Built-in Keyboa  2 u0_a5645  5645  5138  139600 44812 ffffffff b6ea6894 S /system/b2g/b2g
Usage            2 u0_a6313  6313  5138  133480 42136 ffffffff b6ea6894 S /system/b2g/b2g
Find My Device   2 u0_a7362  7362  5138  130904 40420 ffffffff b6ea6894 S /system/b2g/b2g
Browser          2 u0_a7709  7709  5138  136116 43668 ffffffff b6ea6894 S /system/b2g/b2g
(Preallocated a  0 u0_a8226  8226  5138  119248 15760 ffffffff b6ea6a60 S /system/b2g/b2g
(Preallocated a  0 u0_a8248  8248  5138  119248 15588 ffffffff b6ea6a60 S /system/b2g/b2g
root@aries:/ #

Comment 4

[Gregor Wagner [:gwagner]]

Probably not related but I see a bunch of those messages in logcat:
W/Nuwa    ( 5703): Threads remaining at exit:
W/Nuwa    ( 5703):   Chrome_ChildThr (origNativeThreadID=5225 recreatedNativeThreadID=5704)
W/Nuwa    ( 5703):   ImageBridgeChil (origNativeThreadID=5276 recreatedNativeThreadID=5720)
W/Nuwa    ( 5703):   BufferMgrChild (origNativeThreadID=5277 recreatedNativeThreadID=5721)
W/Nuwa    ( 5703): total: 3 outstanding threads. Please fix them so they're destroyed before this point!
W/Nuwa    ( 5703): note: sThreadCount=3, sThreadFreezeCount=18

Comment 5

[Gregor Wagner [:gwagner]]

One more find in logcat from when we hit the assertion:
F/MOZ_Assert( 5131): Assertion failure: get() (dereferencing a UniquePtr containing nullptr), at ../../dist/include/mozilla/UniquePtr.h:286

Comment 6

[Cervantes Yu [:cyu] [:cervantes]]

Attachment: Handle the failures of dispatching a runnable in the NuwaParent protocol actor.

Comment 7

[Cervantes Yu [:cyu] [:cervantes]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=878162d7b429

Comment 8

[Cervantes Yu [:cyu] [:cervantes]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=59ee36d72ecd

Comment 9

[Cervantes Yu [:cyu] [:cervantes]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=a7427572c1f6

Comment 10

[Cervantes Yu [:cyu] [:cervantes]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=6a361b0d4268

Comment 11

[Cervantes Yu [:cyu] [:cervantes]]

(In reply to Cervantes Yu [:cyu] [:cervantes] from comment #10)
> https://treeherder.mozilla.org/#/jobs?repo=try&revision=6a361b0d4268

It turns out that

using namespace base;

in NuwaParent.cpp pollutes CrashReporterParent.cpp and the make windows compiler complain ambiguous usage of vsnprintf() with base::vsnprintf(). Hopefully this should build on Windows.

Comment 12

[Cervantes Yu [:cyu] [:cervantes]]

Attachment: Handle the failures of dispatching a runnable in the NuwaParent protocol actor.

Comment 13

[Cervantes Yu [:cyu] [:cervantes]]

Attachment: Handle the failures of dispatching a runnable in the NuwaParent protocol actor.

Update: fix the build failure on windows.

Comment 14

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Are you sure that we're actually failing to dispatch to the main thread?  That should only fail very very late in shutdown.

Comment 15

[Cervantes Yu [:cyu] [:cervantes]]

From attachment 8647468 [details], the main thread is still running. I don't think it should ever fail dispatching to the main thread. On a closer look I found a race when 2 consecutive NuwaParent::RecvAddNewProcess() messages comes in, but it still doesn't explain the crash in MOZ_ALWAYS_TRUE().

Comment 16

[Cervantes Yu [:cyu] [:cervantes]]

Attachment: A debug instrumentation to trigger a race condition

This simulates that when 2 fork requests (one async, one sync) are on the fly. There is a race to trigger a crash in using mNewProcessFds.

I am not sure if this is the same crash, but this needs to be fixed.

Comment 17

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

So ... should I actually review this patch?

Comment 18

[Cervantes Yu [:cyu] [:cervantes]]

(In reply to Kyle Huey [:khuey] ([e-mail]) from comment #17)
> So ... should I actually review this patch?

No. I'll focus on fixing the race first and request review if there is proof that the crash is in dispatching the runnable.

Comment 19

[Jan Beich]

Nuwa is gone after bug 1284674.