Pending patches for MT-fork stuff

Submitted by Rich Felker on Sept. 28, 2020, 11:37 p.m.

Details

Message ID 20200928233758.GB17637@brightrain.aerifal.cx
State New
Series "Pending patches for MT-fork stuff"
Headers show

Commit Message

Rich Felker Sept. 28, 2020, 11:37 p.m.
On Mon, Sep 28, 2020 at 07:26:15PM -0400, Rich Felker wrote:
> In investigating the MT-fork deadlock stuff and working on a patch
> that makes it attempt to trap rather than deadlocking, I found a
> problem with interaction of fork and aio. A fix for that, along with
> the patch to trap, and a minimal testcase for the aio bug, are
> attached.
> 
> There's also a problematic interaction of abort with fork that was
> just found in glibc that also exists in musl, that I still need to
> fix. I'll follow up later with a proposed solution for that.

And here's the proposed abort fix.
From 000b86dffecf68c1f479e532dcf4e9a403062521 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Mon, 28 Sep 2020 19:30:19 -0400
Subject: [PATCH 4/5] move __abort_lock to its own file and drop pointless
 weak_alias trick

the dummy definition of __abort_lock in sigaction.c was performing
exactly the same role that putting the lock in its own source file
could and should have been used to achieve.

while we're moving it, give it a proper declaration.
---
 src/exit/abort.c            | 2 --
 src/exit/abort_lock.c       | 3 +++
 src/internal/pthread_impl.h | 2 ++
 src/signal/sigaction.c      | 6 ------
 4 files changed, 5 insertions(+), 8 deletions(-)
 create mode 100644 src/exit/abort_lock.c

Patch hide | download patch | download mbox

diff --git a/src/exit/abort.c b/src/exit/abort.c
index e1980f10..f21f458e 100644
--- a/src/exit/abort.c
+++ b/src/exit/abort.c
@@ -6,8 +6,6 @@ 
 #include "lock.h"
 #include "ksigaction.h"
 
-hidden volatile int __abort_lock[1];
-
 _Noreturn void abort(void)
 {
 	raise(SIGABRT);
diff --git a/src/exit/abort_lock.c b/src/exit/abort_lock.c
new file mode 100644
index 00000000..3af72c7b
--- /dev/null
+++ b/src/exit/abort_lock.c
@@ -0,0 +1,3 @@ 
+#include "pthread_impl.h"
+
+volatile int __abort_lock[1];
diff --git a/src/internal/pthread_impl.h b/src/internal/pthread_impl.h
index 23ee566c..21d51be6 100644
--- a/src/internal/pthread_impl.h
+++ b/src/internal/pthread_impl.h
@@ -197,6 +197,8 @@  hidden void __tl_sync(pthread_t);
 
 extern hidden volatile int __thread_list_lock;
 
+extern hidden volatile int __abort_lock[1];
+
 extern hidden unsigned __default_stacksize;
 extern hidden unsigned __default_guardsize;
 
diff --git a/src/signal/sigaction.c b/src/signal/sigaction.c
index c109bea0..a4737404 100644
--- a/src/signal/sigaction.c
+++ b/src/signal/sigaction.c
@@ -7,12 +7,6 @@ 
 #include "lock.h"
 #include "ksigaction.h"
 
-static volatile int dummy_lock[1] = { 0 };
-
-extern hidden volatile int __abort_lock[1];
-
-weak_alias(dummy_lock, __abort_lock);
-
 static int unmask_done;
 static unsigned long handler_set[_NSIG/(8*sizeof(long))];