[Libreoffice-commits] core.git: vcl/headless vcl/inc

[Stephan Bergmann]

 vcl/headless/svpinst.cxx     |   27 ++++++++++++++++++---------
 vcl/inc/headless/svpinst.hxx |    4 ++--
 2 files changed, 20 insertions(+), 11 deletions(-)

New commits:
commit 021bba1b9d9d0e483a76607aaafaf7eb81ff6bed
Author: Stephan Bergmann <sbergman at redhat.com>
Date:   Tue May 10 09:47:04 2016 +0200

    Avoid non--async-signal-safe functions in child after fork
    
    Posix requires that a process forked from a multi-threaded process only calls
    async-signal-safe functions between fork and exec.  This has been observed to
    cause trouble at least in an ASan build, where a forked sub-process (that wants
    to proceed to exec java from getJavaProps,
    jvmfwk/plugins/sunmajor/pluginlib/util.cxx) hangs in
    __sanitizer::BlockingMutex::Lock from within ASan's operator new replacement,
    from within the SAL_INFO in SvpSalInstance::CloseWakeupPipe, from within the
    atfork_child handler established with pthread_atfork.  The rest of the calls in
    SvpSalInstance::Create-/CloseWakupPipe appear to be async-signal-safe.
    
    This pthread_atfork handler got introduced with
    dbced8e8584b631524dacf607f752ebb734901db "Don't share the wakeup pipe with child
    processes".  It is irrelevant when the child process will proceed to call exec.
    And if the child process does not proceed to call exec (which is the intented
    use case why it got added), the above-mentioned Posix requirement makes it look
    unlikely that the child will operate properly (i.e., not call any async-signal-
    safe functions), unless the parent process was single-threaded.
    
    Change-Id: I9ecaf98597b396e0db83fe98fb11a7df7686e1d6

diff --git a/vcl/headless/svpinst.cxx b/vcl/headless/svpinst.cxx
index 5cbcf4a..0305cee 100644
--- a/vcl/headless/svpinst.cxx
+++ b/vcl/headless/svpinst.cxx
@@ -67,8 +67,8 @@ static void atfork_child()
 {
     if (SvpSalInstance::s_pDefaultInstance != nullptr)
     {
-        SvpSalInstance::s_pDefaultInstance->CloseWakeupPipe();
-        SvpSalInstance::s_pDefaultInstance->CreateWakeupPipe();
+        SvpSalInstance::s_pDefaultInstance->CloseWakeupPipe(false);
+        SvpSalInstance::s_pDefaultInstance->CreateWakeupPipe(false);
     }
 }
 
@@ -82,7 +82,7 @@ SvpSalInstance::SvpSalInstance( SalYieldMutex *pMutex ) :
     m_nTimeoutMS            = 0;
 
     m_pTimeoutFDS[0] = m_pTimeoutFDS[1] = -1;
-    CreateWakeupPipe();
+    CreateWakeupPipe(true);
     if( s_pDefaultInstance == nullptr )
         s_pDefaultInstance = this;
 #ifndef ANDROID
@@ -95,29 +95,38 @@ SvpSalInstance::~SvpSalInstance()
     if( s_pDefaultInstance == this )
         s_pDefaultInstance = nullptr;
 
-    CloseWakeupPipe();
+    CloseWakeupPipe(true);
 }
 
-void SvpSalInstance::CloseWakeupPipe()
+void SvpSalInstance::CloseWakeupPipe(bool log)
 {
     if (m_pTimeoutFDS[0] != -1)
     {
-        SAL_INFO("vcl.headless", "CloseWakeupPipe: Closing inherited wakeup pipe: [" << m_pTimeoutFDS[0] << "," << m_pTimeoutFDS[1] << "]");
+        if (log)
+        {
+            SAL_INFO("vcl.headless", "CloseWakeupPipe: Closing inherited wakeup pipe: [" << m_pTimeoutFDS[0] << "," << m_pTimeoutFDS[1] << "]");
+        }
         close (m_pTimeoutFDS[0]);
         close (m_pTimeoutFDS[1]);
         m_pTimeoutFDS[0] = m_pTimeoutFDS[1] = -1;
     }
 }
 
-void SvpSalInstance::CreateWakeupPipe()
+void SvpSalInstance::CreateWakeupPipe(bool log)
 {
     if (pipe (m_pTimeoutFDS) == -1)
     {
-        SAL_WARN("vcl.headless", "Could not create wakeup pipe: " << strerror(errno));
+        if (log)
+        {
+            SAL_WARN("vcl.headless", "Could not create wakeup pipe: " << strerror(errno));
+        }
     }
     else
     {
-        SAL_INFO("vcl.headless", "CreateWakeupPipe: Created wakeup pipe: [" << m_pTimeoutFDS[0] << "," << m_pTimeoutFDS[1] << "]");
+        if (log)
+        {
+            SAL_INFO("vcl.headless", "CreateWakeupPipe: Created wakeup pipe: [" << m_pTimeoutFDS[0] << "," << m_pTimeoutFDS[1] << "]");
+        }
 
         // initialize 'wakeup' pipe.
         int flags;
diff --git a/vcl/inc/headless/svpinst.hxx b/vcl/inc/headless/svpinst.hxx
index 76250b1..f39fefd 100644
--- a/vcl/inc/headless/svpinst.hxx
+++ b/vcl/inc/headless/svpinst.hxx
@@ -92,8 +92,8 @@ public:
     SvpSalInstance( SalYieldMutex *pMutex );
     virtual ~SvpSalInstance();
 
-    void                    CloseWakeupPipe();
-    void                    CreateWakeupPipe();
+    void                    CloseWakeupPipe(bool log);
+    void                    CreateWakeupPipe(bool log);
 
     void                    PostEvent(const SalFrame* pFrame, ImplSVEvent* pData, sal_uInt16 nEvent);