signal handler priority issue

[David Xu]

Sean McNeil wrote:

>On Fri, 2004-06-11 at 15:32, David Xu wrote:
>  
>
>>Sean McNeil wrote:
>>
>>    
>>
>>>On Fri, 2004-06-11 at 07:40, David Xu wrote:
>>> 
>>>
>>>      
>>>
>>>>Sean McNeil wrote:
>>>>
>>>>   
>>>>
>>>>        
>>>>
>>>>>Sorry for top-posting, but it may be easier to read this way....
>>>>>
>>>>>The program below has an optimization bug in that done isn't declare
>>>>>volatile.  With that fixed, it works just fine.  I've been attempting to
>>>>>get boehm-gc working and it seems OK with libc_r, but fails with
>>>>>libpthread.  It is essentially doing what the program below does, but
>>>>>for some reason it gets stuck.  Has anyone else been experimenting with
>>>>>boehm-gc?
>>>>>
>>>>>Also, it would really help if I had a debugger that worked with kse
>>>>>threads.  How is that going?  Tracking down pthread issues right now has
>>>>>been difficult with the current debugger.  Can anyone throw some patches
>>>>>my way that may help?
>>>>>
>>>>>
>>>>>     
>>>>>
>>>>>          
>>>>>
>>>>Please try the patch:
>>>>http://people.freebsd.org/~davidxu/kse/thr_sigsuspend.c.diff
>>>>
>>>>the patch is for file /usr/src/lib/libpthread/thread/thr_sigsuspend.c,
>>>>I believe I caught a bug in the sigsuspend(), thread
>>>>should scan pending signals first, only when there is
>>>>no pending signal in wait set,  the thread can sleep.
>>>>   
>>>>
>>>>        
>>>>
>>>Also, the mask provided by the sigsuspend call should govern what
>>>handlers get called.  So the sigmask should be left in place until after
>>>the _thr_sig_check_pending(curthread) call.
>>>
>>>Thanks for catching this :)
>>>
>>>Sean
>>>
>>>
>>>
>>>
>>> 
>>>
>>>      
>>>
>>No the patch is still not correct, before
>>_thr_sched_switch_unlocked(curthread) returns, signal will be delivered,
>>so there needs a flag to tell signal dispatching code to use old signal mask
>>when delivering signal to signal handler. I am working on it,
>>thanks for your patch.
>>    
>>
>
>What old signal mask?  It should be the signals that sigsuspend allows
>that get handled within sigsuspend.  Make sure the following can still
>happen:
>
>signal is masked.
>sigsuspend is called with signal unmasked.
>signal comes in or is pending already.
>signal handler is called.
>sigsuspend returns.
>
>Sean
>
>
>
>  
>
when signal handler is called in sigsuspend(), thread signal
masks is set to the signal set sigsuspend passes and ored with
the signal current is being handled.  uc_sigmask in ucontext is
set to the signal masks before sigsuspend is called, when the
signal handler is returned, uc_sigmask should be copied to
thread's signal mask, then sigsuspend returns. your patch
does not set uc_sigmasks correctly.

David Xu