From: Ken Dreyer <kdreyer@redhat.com>
Date: Mon, 18 Jul 2022 19:06:06 +0000 (-0400)
Subject: build: fix atomic linking with LTO on s390x
X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=0e07d965f93dd9f2606d541f26cfd050cc4c1e54;p=ceph.git

build: fix atomic linking with LTO on s390x

Prior to this change, Fedora and RHEL 9 on s390x would incorrectly pass
the HAVE_CXX11_ATOMIC check. As a consequence, the rest of Ceph would
fail to link because of missing atomic methods "__atomic_load_16",
"__atomic_store_16", "__atomic_compare_exchange_16".

Mark this method so that it is not optimized out, even with LTO. With
this change, s390x properly fails HAVE_CXX11_ATOMIC and falls back to
HAVE_LIBATOMIC.

Move the "BuildRequires: libatomic" RPM line out from the seastar+fedora
conditional and into the main fedora+rhel conditional so that the
HAVE_LIBATOMIC check will pass.

Fixes: https://tracker.ceph.com/issues/54514
Fixes: https://tracker.ceph.com/issues/56492

Co-authored-by: Kaleb S. Keithley <kkeithle@redhat.com>
Signed-off-by: Ken Dreyer <kdreyer@redhat.com>
---

diff --git a/ceph.spec.in b/ceph.spec.in
index 9f522a750b786..c0806afaf7a85 100644
--- a/ceph.spec.in
+++ b/ceph.spec.in
@@ -311,7 +311,6 @@ BuildRequires:  systemtap-sdt-devel
 %if 0%{?fedora}
 BuildRequires:  libubsan
 BuildRequires:  libasan
-BuildRequires:  libatomic
 %endif
 %if 0%{?rhel}
 BuildRequires:  gcc-toolset-9-annobin
@@ -353,6 +352,7 @@ Requires:	systemd
 BuildRequires:  boost-random
 BuildRequires:	nss-devel
 BuildRequires:	keyutils-libs-devel
+BuildRequires:  libatomic
 BuildRequires:	libibverbs-devel
 BuildRequires:  librdmacm-devel
 BuildRequires:  ninja-build
diff --git a/cmake/modules/CheckCxxAtomic.cmake b/cmake/modules/CheckCxxAtomic.cmake
index 78c0f988707a0..ac697553f08b3 100644
--- a/cmake/modules/CheckCxxAtomic.cmake
+++ b/cmake/modules/CheckCxxAtomic.cmake
@@ -24,7 +24,14 @@ function(check_cxx_atomics var)
 // We specifically test access via an otherwise unknown pointer here
 // to ensure we get the most complex case.  If this access can be
 // done without libatomic, then all accesses can be done.
+struct tagged_ptr {
+  int* ptr;
+  std::size_t tag;
+};
+
 bool atomic16(std::atomic<unsigned __int128> *ptr)
+void atomic16(std::atomic<tagged_ptr> *ptr) __attribute__ ((used));
+void atomic16(std::atomic<tagged_ptr> *ptr)
 {
   return *ptr != 0;
 }