Dear Tobias,
Thank you for all the great information. This enabled me to isolate the
change which caused the issue.
So, for a bit of background, SWORD has no calls to mark critical
sections which might be problematic for re-entrant usage. This has been
due to the many implementations of threading across many different
platforms over the years, before C++11. But, as a policy to support
clients which desire to use SWORD in a multithreaded manner, we do our
best to make this safe by advising clients to use separate SWMgr
instances per thread. There are still some shared objects in this
scenario, but we do our best to do all the writing to these shared
objects upon initialization. We broke this rule in commit 2760, which is
what caused your problem. SWORD have a facility to pool open file
handles, to help OSs which have small open file handle limits. This
work is done in FileMgr. Recently, to support Windows Unicode path
names (the commit you found which breaks your multithreaded use), we
rounded up all remaining native file IO calls and replaced them to used
FileMgr for the IO and then extended FileMgr to handle Windows Unicode
paths in a Windows-specific manner. One of these changes was in
CURLFTPTransport, which is where you are having the issue. The problem
is that, where previously this class was directly opening a FILE to do
its writing, commit 2760 changed this to use FileMgr to open the file,
which involved the SWORD-wide file handle pool, and since we are create
a new file, we are always writing to this shared pool container, which
is not threadsafe. My guess is that you have two threads trying to
update the pool container at exactly the same time. Using the file
handle pool is usually safe, because SWMgr "opens" all of its file
handles on initialization (these are not actually opening OS file
handles, but instead updating the file handle pool container with proxy
objects which delay actual OS open to on-demand, but the point is this
instance of shared file handle pool container writing is done on
creation of the SWMgr, afterward, the shared resource file handle pool
is only read and each object in the pool is owned by only 1 thread if
the "each thread must have its own SWMgr" rule is followed.
Regardless of the details. I believe I have committed a fix for you.
In short, I have changed CURLFTPTransport to follow our rule to avoid
writing to shared objects when we might be re-entrant. Here we now use
FileMgr's methods which isolate OS implementation, but not FileMgr's
file handle pool (as it did not previously use the pool before this
commit). This should allow this to still take advantage of the Windows
OS-specific implementation, and also avoid the critical section. Can
you please try SVN head and let me know if we are back to 20 out of 20
successes?
Thanks again for the very helpful debug log and exact revision where
failure began.
Troy
On 10/13/20 10:08 PM, Tobias Klein wrote:
I managed to get a backtrace to a segmentation fault using GDB.
It seems like the crash is happening in sword::FileMgr::open( ...
The starting point is sword::InstallMgr::refreshRemoteSource as I was
writing before.
Best regards,
Tobias
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7f1af3fff700 (LWP 220833)]
0x00007f1b027045a4 in sword::FileMgr::open(char const*, int, int,
bool) () from
/home/tobi/dev/ezra_project/node-sword-interface-git/build/Release/node_sword_interface.node
(gdb) backtrace
#0 0x00007f1b027045a4 in sword::FileMgr::open(char const*, int, int,
bool) () from
/home/tobi/dev/ezra_project/node-sword-interface-git/build/Release/node_sword_interface.node
#1 0x00007f1b0276ad7b in sword::(anonymous
namespace)::my_fwrite(void*, unsigned long, unsigned long, void*) ()
from
/home/tobi/dev/ezra_project/node-sword-interface-git/build/Release/node_sword_interface.node
#2 0x00007f1b180626bf in ?? () from
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#3 0x00007f1b18074a2b in ?? () from
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#4 0x00007f1b1807e2e4 in ?? () from
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#5 0x00007f1b1807f6f9 in curl_multi_perform () from
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#6 0x00007f1b18075d13 in curl_easy_perform () from
/usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#7 0x00007f1b0276b683 in sword::CURLFTPTransport::getURL(char const*,
char const*, sword::SWBuf*) () from
/home/tobi/dev/ezra_project/node-sword-interface-git/build/Release/node_sword_interface.node
#8 0x00007f1b0271d5d2 in
sword::InstallMgr::remoteCopy(sword::InstallSource*, char const*, char
const*, bool, char const*) ()
from
/home/tobi/dev/ezra_project/node-sword-interface-git/build/Release/node_sword_interface.node
#9 0x00007f1b0271edc7 in
sword::InstallMgr::refreshRemoteSource(sword::InstallSource*) () from
/home/tobi/dev/ezra_project/node-sword-interface-git/build/Release/node_sword_interface.node
#10 0x00007f1b026ad734 in
RepositoryInterface::refreshIndividualRemoteSource(std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> >, std::function<void
(unsigned int)>*) ()
from
/home/tobi/dev/ezra_project/node-sword-interface-git/build/Release/node_sword_interface.node
#11 0x00007f1b026b17dd in
std::thread::_State_impl<std::thread::_Invoker<std::tuple<int
(RepositoryInterface::*)(std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> >, std::function<void
(unsigned int)>*), RepositoryInterface*,
std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> >, std::function<void (unsigned int)>*> >
>::_M_run() ()
from
/home/tobi/dev/ezra_project/node-sword-interface-git/build/Release/node_sword_interface.node
#12 0x00007f1b1d622cb4 in ?? () from
/usr/lib/x86_64-linux-gnu/libstdc++.so.6
#13 0x00007f1b1e20a609 in start_thread () from
/lib/x86_64-linux-gnu/libpthread.so.0
#14 0x00007f1b1e131103 in clone () from /lib/x86_64-linux-gnu/libc.so.6
On 10/13/20 1:07 PM, Tobias Klein wrote:
Hi Troy,
I tested more SVN revisions of SWORD trunk (starting from my stable
version until I hit the bug) and I can now say that
SVN Rev. 3759 is the last SVN revision that works without hanging for
the below mentioned scenario. (20 out of 20 tests successful)
SVN Rev. 3760 is the first SVN revision where the hanging occurs. The
commit message is "First cut at better isolation of FileIO to FileMgr
and providing a WIN32 impl with works with wchar_t".
Modified files:
include/filemgr.h
include/swbuf.h
lib/bcppmake/libsword.bpr
src/mgr/curlftpt.cpp
src/mgr/curlhttpt.cpp
src/mgr/filemgr.cpp
src/mgr/installmgr.cpp
src/mgr/swmgr.cpp
src/utilfuns/utilstr.cpp
Maybe this helps to find the root-cause.
Best regards,
Tobias
On 10/12/20 9:20 PM, Tobias Klein wrote:
I'll see whether I can collect a stack trace. It may take some time
until I have it.
The multi-threaded "remote source refreshing" worked without issues
until recently.
Here is the code of the function that does the actual work in a thread.
See
https://github.com/tobias-klein/node-sword-interface/blob/787160ccb4b3bab2a762d22f74031c7237edc803/src/sword_backend/repository_interface.cpp#L105.
intRepositoryInterface::refreshIndividualRemoteSource(stringremoteSourceName,
std::function<void(unsignedintprogress)>*progressCallback)
{
//cout << "Refreshing source " << remoteSourceName << endl << flush;
InstallSource* source= this->getRemoteSource(remoteSourceName);
intresult= this->_installMgr->refreshRemoteSource(source);
if(result!= 0) {
cerr<<"Failed to refresh source "<<remoteSourceName<<endl<<flush;
}
remoteSourceUpdateMutex.lock();
this->_remoteSourceUpdateCount++;
unsignedinttotalPercent=
(unsignedint)calculateIntPercentage<double>(this->_remoteSourceUpdateCount,
this->_remoteSourceCount);
if(progressCallback!= 0) {
(*progressCallback)(totalPercent);
}
remoteSourceUpdateMutex.unlock();
returnresult;
}
Best regards,
Tobias
On 10/12/20 9:01 PM, Troy A. Griffitts wrote:
Any luck getting a stack trace on crash?
Regarding the "multitheaded mode", I'd have to get a bit more
information as to exactly how you are sharing SWORD objects across
your threads. Generally, as a rule, you shouldn't. We recommend a
separate instance of SWMgr per thread and that probably goes for
InstallMgr, as well.
Troy
On October 12, 2020 8:29:31 PM GMT+02:00, Tobias Klein
<cont...@tklein.info> wrote:
Hi Troy,
I'm using curl on all three platforms.
Regarding the timeout configuration I have not changed anything
yet, to make this configurable in Ezra Project is still on my
todo list.
I just checked on Linux.
With the old version (May 18th 2020) no hanging or crash in 10
out of 10 times.
WIth the new version (latest trunk / SWORD 1.9 RC3) I get 1 x
crash, 2 x hanging, 7 x working.
I'm running the InstallMgr::refreshRemoteSource "in a
multi-threaded mode".
Best regards,
Tobias
On 10/12/20 6:59 PM, Troy A. Griffitts wrote:
Hi Tobias,
What transport library are you building with? ftplib or curl?
Have you changed the value of our new timeout from the
default, I believe we decided on, 10 seconds?
Troy
On October 12, 2020 6:46:54 PM GMT+02:00, Tobias Klein
<cont...@tklein.info> wrote:
Hi Troy,
In my latest Ezra Project builds using SWORD trunk I’ve been noticing random
„hangs“ and crashes related to "updating remote sources“. I suppose it must be
around InstallMgr::refreshRemoteSource.
This was still rock solid when using SWORD trunk from May 18th 2020,
but not so any more with the recent SWORD trunk.
Unfortunately I cannot pinpoint this more specifically. I just wanted
to first share this observation, because it’s worrying me.
I’ve been noticing this regression both on Windows and macOS. Need to
check later whether this also happens on Linux, cannot recall it right now.
Best regards,
Tobias
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