svn commit: r212076 - head/lib/libthr/thread

[David Xu]

Kostik Belousov wrote:
> On Wed, Sep 01, 2010 at 02:18:33AM +0000, David Xu wrote:
>> Author: davidxu
>> Date: Wed Sep  1 02:18:33 2010
>> New Revision: 212076
>> URL: http://svn.freebsd.org/changeset/base/212076
>>
>> Log:
>>   Add signal handler wrapper, the reason to add it becauses there are
>>   some cases we want to improve:
>>     1) if a thread signal got a signal while in cancellation point,
>>        it is possible the TDP_WAKEUP may be eaten by signal handler
>>        if the handler called some interruptibly system calls.
>>     2) In signal handler, we want to disable cancellation.
>>     3) When thread holding some low level locks, it is better to
>>        disable signal, those code need not to worry reentrancy,
>>        sigprocmask system call is avoided because it is a bit expensive.
>>   The signal handler wrapper works in this way:
>>     1) libthr installs its signal handler if user code invokes sigaction
>>        to install its handler, the user handler is recorded in internal
>>        array.
>>     2) when a signal is delivered, libthr's signal handler is invoke,
>>        libthr checks if thread holds some low level lock or is in critical
>>        region, if it is true, the signal is buffered, and all signals are
>>        masked, once the thread leaves critical region, correct signal
>>        mask is restored and buffered signal is processed.
>>     3) before user signal handler is invoked, cancellation is temporarily
>>        disabled, after user signal handler is returned, cancellation state
>>        is restored, and pending cancellation is rescheduled.
> 
>> +static void
>> +thr_sighandler(int sig, siginfo_t *info, void *_ucp)
>> +{
> 
>> +	if ((actp->sa_flags & SA_SIGINFO) != 0)
>> +		(*(sigfunc))(sig, info, ucp);
>> +	else {
>> +		((ohandler)(*sigfunc))(
>> +			sig, info->si_code, (struct sigcontext *)ucp,
>> +			info->si_addr, (__sighandler_t *)sigfunc);
>> +	}
> 
> I do not think this is very important, but freebsd old-style signal
> handler fourth argument is usually the faulted %eip value. This is
> most likely irrelevant for any source that is linked with libthr.so
> new enough to contain this change.

Isn't the si_addr in siginfo a fault address ? I remembered I saved
the fault address in ksiginfo_t which is converted to userland
siginfo, and fault address should be there. what's wrong here ?