On Apr 3 13:51, Jon TURNEY wrote:
On 03/04/2015 13:17, Corinna Vinschen wrote:
On Apr 3 13:18, Corinna Vinschen wrote:
On Apr 2 20:30, Jon TURNEY wrote:
sigset_t this_oldmask = set_process_mask_delta ();
- thiscontext.uc_sigmask = this_oldmask;
+ context.uc_sigmask = this_oldmask;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This call to set_process_mask_delta() should occur before constructing
the context, so that filling in uc_sigmask can be moved into the above
`'if' branch.
Ok, I will move it.
On second thought, isn't this slightly wrong anyway? Shouldn't that be
context.uc_sigmask = _my_tls.sigmask;
context.uc_mcontext.oldmask = this_oldmask;
As I wrote elsewhere: You'll have to help me understand what the difference
in meaning between ucontext_t.uc_sigmask and ucontext_t.uc_mcontext.oldmask
is.
I don't see how the value of _my_tls.sigmask has any meaning at that point
in the code.
Ok, I had a look into the Linux source and searched the web, and here's
the problem.
One is that sigset_t on Linux is not just a 32 or 64 bit bitmask anymore,
but an array of ulong's used as a rather big sigmask.
OTOH, mcontext_t::oldmask is only the size of "unsigned long". In fact,
as it turns out by inspecting the Linux kernel, oldmask is nothing else
than the first bits of uc_sigmask which fit into an unsigned long. And
in the net I found that oldmask is just the old representation of
sigset_t, before the Linux kernel allowed more signals than fit into
a bitmask of unsigned long size. In fact, it's only for backward compat,
but unused these days.
Given that, setting context.uc_sigmask to this_oldmask is apparently
the right thing to do. For emulating backward compat (which we don't
need, but it also doesn't hurt), we could set oldmask to the same
value:
context.uc_sigmask = context.uc_mcontext.oldmask = this_oldmask;