system/musl: fix PPC64 atomics

2 files changed, 77 insertions, 1 deletions

diff --git a/system/musl/APKBUILD b/system/musl/APKBUILD
index 867af507c..a3a0eb81c 100644
--- a/system/musl/APKBUILD
+++ b/system/musl/APKBUILD
@@ -2,7 +2,7 @@
 # Maintainer: A. Wilcox <awilfox@adelielinux.org>
 pkgname=musl
 pkgver=1.1.20
-pkgrel=2
+pkgrel=3
 pkgdesc="System library (libc) implementation"
 url="http://www.musl-libc.org/"
 arch="all"
@@ -26,6 +26,7 @@ source="http://www.musl-libc.org/releases/musl-$pkgver.tar.gz
 	fix-file-locking-race.patch
 	dcngettext-null-deref.patch
 	getaddrinfo-regression.patch
+	ppc64-atomic.patch
 
 	ldconfig
 	getent.c
@@ -120,6 +121,7 @@ sha512sums="d3a7a30aa375ca50d7dcfbd618581d59e1aa5378417f50a0ca5510099336fd74cc9d
 b967339d9048161583523e847be91779adb0e16cc225d6ff85ef51748269b2dab08a0b8e558ad01469135837a9df76a59bf9a31791dd4063d75bc5efe6e94861  fix-file-locking-race.patch
 a08d1b170356beea333ace1da12f8a8399ca80c5d9c32ff2fcd8562537a670214f566e4b1219a11b32129078e22fbf7009bb277b7de8550a89352a64b3b5090d  dcngettext-null-deref.patch
 e3953a3a73ef11696dd3eb216e18b152ae35198d8bff686d157e27bc90fb558f9a0be518025a90534e9afd6ea1bf731ffdb6fcb202bb9368f2c8eec7ca886141  getaddrinfo-regression.patch
+aae9110eccb8cd7dcd3c957fcb01ed524598f79f7fa1a16b9993af40793545d1ec211e7e6aeabe7af7715d94cc26a473ea0acf6d6e66019bf65f03d4b8e24a4b  ppc64-atomic.patch
 cce2f1eeb61e55674469c26871a573cce61d739c3defe9c8f56f2b774f6ba5435849ad542a6714120efddc98c297098e9c98a1a424ac593df2243d4aa479f9a9  ldconfig
 378d70e65bcc65bb4e1415354cecfa54b0c1146dfb24474b69e418cdbf7ad730472cd09f6f103e1c99ba6c324c9560bccdf287f5889bbc3ef0bdf0e08da47413  getent.c
 9d42d66fb1facce2b85dad919be5be819ee290bd26ca2db00982b2f8e055a0196290a008711cbe2b18ec9eee8d2270e3b3a4692c5a1b807013baa5c2b70a2bbf  iconv.c"
diff --git a/system/musl/ppc64-atomic.patch b/system/musl/ppc64-atomic.patch
new file mode 100644
index 000000000..6e96a9048
--- /dev/null
+++ b/system/musl/ppc64-atomic.patch
@@ -0,0 +1,74 @@
+From 12817793301398241b6cb00c740f0d3ca41076e9 Mon Sep 17 00:00:00 2001
+From: Rich Felker <dalias@aerifal.cx>
+Date: Fri, 14 Sep 2018 10:47:16 -0400
+Subject: fix broken atomic store on powerpc[64]
+
+in our memory model, all atomics are supposed to be full barriers;
+stores are not release-only. this is important because store is used
+as an unlock operation in places where it needs to acquire the waiter
+count to determine if a futex wake is needed. at least in the
+malloc-internal locks, but possibly elsewhere, soft deadlocks from
+missing futex wake (breakable by poking the threads to restart the
+syscall, e.g. by attaching a tracer) were reported to occur.
+
+once the malloc lock is replaced with Jens Gustedt's new lock
+implementation (see commit 47d0bcd4762f223364e5b58d5a381aaa0cbd7c38),
+malloc will not be affected by the issue, but it's not clear that
+other uses won't be. reducing the strength of the ordering properties
+required from a_store would require a thorough analysis of how it's
+used.
+
+to fix the problem, I'm removing the powerpc[64]-specific a_store
+definition; now, the top-level atomic.h will implement a_store using
+a_barrier on both sides of the store.
+
+it's not clear to me yet whether there might be issues with the other
+atomics. it's possible that a_post_llsc needs to be replaced with a
+full barrier to guarantee the formal semanics we want, but either way
+I think the difference is unlikely to impact the way we use them.
+---
+ arch/powerpc/atomic_arch.h   | 8 --------
+ arch/powerpc64/atomic_arch.h | 8 --------
+ 2 files changed, 16 deletions(-)
+
+diff --git a/arch/powerpc/atomic_arch.h b/arch/powerpc/atomic_arch.h
+index 5b65cde7..c2673919 100644
+--- a/arch/powerpc/atomic_arch.h
++++ b/arch/powerpc/atomic_arch.h
+@@ -30,14 +30,6 @@ static inline void a_post_llsc()
+ 	__asm__ __volatile__ ("isync" : : : "memory");
+ }
+ 
+-#define a_store a_store
+-static inline void a_store(volatile int *p, int v)
+-{
+-	a_pre_llsc();
+-	*p = v;
+-	a_post_llsc();
+-}
+-
+ #define a_clz_32 a_clz_32
+ static inline int a_clz_32(uint32_t x)
+ {
+diff --git a/arch/powerpc64/atomic_arch.h b/arch/powerpc64/atomic_arch.h
+index 17cababd..2bed82be 100644
+--- a/arch/powerpc64/atomic_arch.h
++++ b/arch/powerpc64/atomic_arch.h
+@@ -48,14 +48,6 @@ static inline void a_post_llsc()
+ 	__asm__ __volatile__ ("isync" : : : "memory");
+ }
+ 
+-#define a_store a_store
+-static inline void a_store(volatile int *p, int v)
+-{
+-	a_pre_llsc();
+-	*p = v;
+-	a_post_llsc();
+-}
+-
+ #define a_crash a_crash
+ static inline void a_crash()
+ {
+-- 
+cgit v1.2.1
+