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

[Kostik Belousov]

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.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 196 bytes
Desc: not available
Url : http://lists.freebsd.org/pipermail/svn-src-head/attachments/20100902/bb49430a/attachment.pgp