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Re: Daemon taking 100% cpu
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Re: Daemon taking 100% cpu

  • Subject: Re: Daemon taking 100% cpu
  • From: Arjun SM <email@hidden>
  • Date: Fri, 17 May 2013 20:30:40 +0530
Thanks for your reply Quinn,
I would look more on the pointers you have given.

 Also I wanted to understand if calling SCDynamicStoreCopyConsoleUser() in my daemon has caused a memory access exception (SIGSEGV or SIGBUS) ?

I probably would not use this function anymore and look for some other ways of knowing if a user has logged in.

thanks,
~Arjun


On Fri, May 17, 2013 at 4:55 PM, Quinn "The Eskimo!" <email@hidden> wrote:

On 17 May 2013, at 10:46, Arjun SM <email@hidden> wrote:

> I have an issue with my daemon taking 100% cpu when left overnight. (Daemon undergoing stress testing at the moment). I am unable to narrow down the issue.

The daemon is triggering a memory access exception (SIGSEGV or SIGBUS) when freeing memory (tiny_malloc_from_free_list), which it catches as a signal (_sigtramp), and in the signal handler it call APIs that aren't signal safe (std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, std::allocator<char> const&)) which then deadlock.

The list of APIs that are guaranteed to be signal safe is vanishingly small; see <x-man-page://2/sigaction> for details.

My best guess is that you have your own in-process crash reporter.  That's a bad idea in general, and seems to be the cause of this hang.  If you didn't catch the signal, it would've been caught by the system-wide out-of-process crash reporter, which would give you a nice crash log.

Share and Enjoy
--
Quinn "The Eskimo!"                    <http://www.apple.com/developer/>
Apple Developer Relations, Developer Technical Support, Core OS/Hardware



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 >Daemon taking 100% cpu (From: Arjun SM <email@hidden>)
 >Re: Daemon taking 100% cpu (From: "Quinn \"The Eskimo!\"" <email@hidden>)

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