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-rw-r--r--glibc/signal/signal_thread.mdwn45
1 files changed, 42 insertions, 3 deletions
diff --git a/glibc/signal/signal_thread.mdwn b/glibc/signal/signal_thread.mdwn
index c6e8d69..544d387 100644
--- a/glibc/signal/signal_thread.mdwn
+++ b/glibc/signal/signal_thread.mdwn
@@ -13,12 +13,11 @@ invoker of `kill` to the target process. The target process' [[signal_thread]]
job is it to listen to such messages and to set up signal handler contexts in
other threads.
----
-
-[[!tag open_issue_documentation]]
# IRC, freenode, #hurd, 2011-04-20
+[[!tag open_issue_documentation]]
+
<braunr> bugs around signals are very tricky
<braunr> signals are actually the most hairy part of the hurd
<braunr> and the reason they're aynchronous is that they're handled by a
@@ -50,3 +49,43 @@ other threads.
<braunr> mach and the hurd were intended to be "hyperthreaded"
[[open_issues/multithreading]].
+
+
+# IRC, freenode, #hurd, 2013-09-17
+
+ <teythoon> I just realized that I know next to nothing about signal
+ handling on the Hurd...
+ <teythoon> especially /hurd/inits role in it
+ <teythoon> reading glibcs kill.c it does not involve /hurd/init at all, but
+ /hurd/init is full of proxying code for the msg protocol
+ <teythoon> ah, /hurd/init mitms the signal handling logic in the libc for
+ its own signals
+ <teythoon> for msg_sig_post it sends a reply immediately, and then
+ processes the signal, I wonder why that is done
+ <teythoon> also it "forwards" any signals it receives to the child it
+ spawned (like /etc/hurd/runsystem), I wonder why...
+ <teythoon> good thing the comments tell what is done, not why...
+ <teythoon> so in theory kill -HUP 1 should have been forwarded to the
+ "runsystem" process, I wonder why that does not work if that one execs
+ sysvinit
+ <braunr> teythoon: can't help you there :/
+ <teythoon> braunr: I think I sorted it out on my own, we'll see how that
+ works out in practice ;)
+ <braunr> good
+
+
+## IRC, freenode, #hurd, 2013-09-18
+
+ <teythoon> braunr: I figured out why /hurd/init does this strange thing
+ with the msg protocol
+ <teythoon> braunr: it has no signal thread
+ <teythoon> I wonder how /hurd/exec and the initial filesystem handle
+ this...
+ <teythoon> err, afaics the signal thread is created in fork(), so any
+ process not created using it (ie manually using task_create) should lack
+ the signal thread, no?
+ <teythoon> that'd be the root fs, /hurd/{exec,init,auth,proc} and
+ /etc/hurd/runsystem (the child started by /hurd/init)
+ <teythoon> but I see only /hurd/init doing something about it, namely
+ setting a msgport and handling the msg protocol, relaying any messages to
+ the signal handling logic in the glibc