It has been possible for a signal to arrive in between us checking
g_interrupted and exiting - sucessfully, even though we were interrupted.
This way, if a signal arrives before we reset the disposition, we
will reliably check for it later; if it arrives afterwards, it'll
kill us automatically.
No difference in practice, but it's tidier and protects us
if we ever use g_interrupted earlier in main -- in that case,
the compiler might chose to keep the variable in a register without
the volatile.
Found by @bugaevc, thanks!
With this, hitting ctrl-c twice in `for i in $(seq 10) { sleep 1 }`
terminates the loop as expected (...well, I'd expect it to quit after
just one ctrl-c, but serenity's shell makes a single ctrl-c only
quit the current loop iteration).
Part of #3419.
* In some cases, we can first call sigaction()/signal(), then *not* pledge
sigaction.
* In other cases, we pledge sigaction at first, call sigaction()/signal()
second, then pledge again, this time without sigaction.
* In yet other cases, we keep the sigaction pledge. I suppose these could all be
migrated to drop it or not pledge it at all, if somebody is interested in
doing that.
As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
This was a workaround to be able to build on case-insensitive file
systems where it might get confused about <string.h> vs <String.h>.
Let's just not support building that way, so String.h can have an
objectively nicer name. :^)
This is dirty but pretty cool! If we have a pending, unmasked signal for
a process that's blocked inside the kernel, we set up alternate stacks
for that process and unblock it to execute the signal handler.
A slightly different return trampoline is used here: since we need to
get back into the kernel, a dedicated syscall is used (sys$sigreturn.)
This restores the TSS contents of the process to the state it was in
while we were originally blocking in the kernel.
NOTE: There's currently only one "kernel resume TSS" so signal nesting
definitely won't work.