I'm somewhat concerned about following scenario: File file_obj(...); LockFile lock (file_obj.GetDescriptor ()); ..
My understanding, that on Windows if LockFile duplicates original handle (i.e. file.GetDescriptor ()) only a duplicated handle will be allowed to call IO functions on this file within locked region, meanwhile file_obj will be blocked on IO. If LockFile just holds a reference to original handle then file_obj can proceed on IO operations in exclusive mode. In order to make it clear that LockFile references File we can make LockFile to take File& as constructor parameter instead of a raw handle. On Thu, May 21, 2015 at 10:28 AM, Zachary Turner <ztur...@google.com> wrote: > Why does someone other than the LockFile object care about holding a raw > handle? Shouldn't it just hold a reference/pointer to the LockFile? > On Thu, May 21, 2015 at 10:06 AM Oleksiy Vyalov <ovya...@google.com> > wrote: > >> Windows file lock is tied to a file handle - using handle duplication >> effectively applies locking on duplicated handle, not on original, so your >> original handle will be blocked on IO trying to read/write. >> Maybe we can just eliminate CloseHandle call ( >> https://github.com/llvm-mirror/lldb/blob/master/source/Host/windows/LockFileWindows.cpp#L50) >> if file will be eventually closed by LockFileWindows caller. >> >> On Thu, May 21, 2015 at 9:58 AM, Zachary Turner <ztur...@google.com> >> wrote: >> >>> I don't experience this crash but looking at the proposed fix it >>> certainly seems like a plausible explanation. Seems to me like something >>> should transfer ownership though rather than duplicating the handle >>> >>> On Thu, May 21, 2015 at 9:52 AM Colin Riley <co...@codeplay.com> wrote: >>> >>>> Windows 7 64, Debug, latest vs13. >>>> >>>> >>>> On 21/05/2015 17:39, Oleksiy Vyalov wrote: >>>> >>>> Hi Colin, >>>> >>>> could you give more context about crash - what build configuration do >>>> you use (debug, release,..) and which OS? >>>> I'm running this code on Windows 7 and haven't noticed any failures. >>>> >>>> >>>> On Thu, May 21, 2015 at 8:57 AM, Colin Riley <co...@codeplay.com> >>>> wrote: >>>> >>>>> >>>>> Zachary, do you see this on windows at all? Tip for us results in >>>>> crashes when releasing file descriptors without the below fix. >>>>> >>>>> Colin >>>>> >>>>> >>>>> On 19/05/2015 12:52, Aidan Dodds wrote: >>>>> >>>>> Hi, >>>>> >>>>> We have been seeing a crash on windows when connecting to an android >>>>> target using lldb-server. >>>>> I am not sure if this affects other platforms too. >>>>> I think this was introduced with http://reviews.llvm.org/D9056. >>>>> >>>>> I tracked the crash back to the workings of ModuleCache::GetAndPut(). >>>>> >>>>> The crash seems to be due to a file descriptor being released twice, >>>>> once by the original "File lock_file" and again by the "LockFile lock" who >>>>> share the same file descriptor. >>>>> >>>>> The file descriptor sharing happens because of this line: >>>>> ModuleCache.cpp @ 164 >>>>> LockFile lock (lock_file.GetDescriptor ()); >>>>> >>>>> Both destructors attempt to release effectively the same file >>>>> descriptor. I was able to fix the crash by duplicating the file handle in >>>>> the lock file constructor using _dup(). (patch attached) >>>>> I wasn't sure if this was the right fix however. Has anyone else seen >>>>> this? >>>>> Should "File lock_file" perhaps transfer its file descriptor >>>>> completely rather then share it? >>>>> >>>>> Thanks, >>>>> Aidan >>>>> >>>>> >>>>> _______________________________________________ >>>>> lldb-dev mailing >>>>> listlldb-...@cs.uiuc.eduhttp://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev >>>>> >>>>> >>>>> -- >>>>> - Colin Riley >>>>> Senior Director, >>>>> Parallel/Graphics Debugger Systems >>>>> >>>>> Codeplay Software Ltd >>>>> 45 York Place, Edinburgh, EH1 3HP >>>>> Tel: 0131 466 0503 >>>>> Fax: 0131 557 6600 >>>>> Website: http://www.codeplay.com >>>>> Twitter: https://twitter.com/codeplaysoft >>>>> >>>>> This email and any attachments may contain confidential and /or >>>>> privileged information and is for use by the addressee only. If you are >>>>> not the intended recipient, please notify Codeplay Software Ltd >>>>> immediately and delete the message from your computer. You may not copy >>>>> or forward it,or use or disclose its contents to any other person. Any >>>>> views or other information in this message which do not relate to our >>>>> business are not authorized by Codeplay software Ltd, nor does this >>>>> message form part of any contract unless so stated. >>>>> As internet communications are capable of data corruption Codeplay >>>>> Software Ltd does not accept any responsibility for any changes made to >>>>> this message after it was sent. Please note that Codeplay Software Ltd >>>>> does not accept any liability or responsibility for viruses and it is >>>>> your responsibility to scan any attachments. >>>>> Company registered in England and Wales, number: 04567874 >>>>> Registered office: 81 Linkfield Street, Redhill RH1 6BY >>>>> >>>>> >>>> >>>> >>>> -- >>>> Oleksiy Vyalov | Software Engineer | ovya...@google.com >>>> >>>> >>>> -- >>>> - Colin Riley >>>> Senior Director, >>>> Parallel/Graphics Debugger Systems >>>> >>>> Codeplay Software Ltd >>>> 45 York Place, Edinburgh, EH1 3HP >>>> Tel: 0131 466 0503 >>>> Fax: 0131 557 6600 >>>> Website: http://www.codeplay.com >>>> Twitter: https://twitter.com/codeplaysoft >>>> >>>> This email and any attachments may contain confidential and /or privileged >>>> information and is for use by the addressee only. If you are not the >>>> intended recipient, please notify Codeplay Software Ltd immediately and >>>> delete the message from your computer. You may not copy or forward it,or >>>> use or disclose its contents to any other person. Any views or other >>>> information in this message which do not relate to our business are not >>>> authorized by Codeplay software Ltd, nor does this message form part of >>>> any contract unless so stated. >>>> As internet communications are capable of data corruption Codeplay >>>> Software Ltd does not accept any responsibility for any changes made to >>>> this message after it was sent. Please note that Codeplay Software Ltd >>>> does not accept any liability or responsibility for viruses and it is your >>>> responsibility to scan any attachments. >>>> Company registered in England and Wales, number: 04567874 >>>> Registered office: 81 Linkfield Street, Redhill RH1 6BY >>>> >>>> >> >> >> -- >> Oleksiy Vyalov | Software Engineer | ovya...@google.com >> > -- Oleksiy Vyalov | Software Engineer | ovya...@google.com
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