Save errno in signal handlers

base/daemon/src/BaseDaemon.cpp

@@ -88,10 +88,14 @@ using signal_function = void(int, siginfo_t*, void*);
 
 static void writeSignalIDtoSignalPipe(int sig)
 {
+    auto saved_errno = errno;   /// We must restore previous value of errno in signal handler.
+
     char buf[buf_size];
     DB::WriteBufferFromFileDescriptor out(signal_pipe.fds_rw[1], buf_size, buf);
     DB::writeBinary(sig, out);
     out.next();
+
+    errno = saved_errno;
 }
 
 /** Signal handler for HUP / USR1 */
@@ -110,6 +114,8 @@ static void terminateRequestedSignalHandler(int sig, siginfo_t * info, void * co
   */
 static void signalHandler(int sig, siginfo_t * info, void * context)
 {
+    auto saved_errno = errno;   /// We must restore previous value of errno in signal handler.
+
     char buf[buf_size];
     DB::WriteBufferFromFileDescriptorDiscardOnFailure out(signal_pipe.fds_rw[1], buf_size, buf);
 
@@ -134,6 +140,8 @@ static void signalHandler(int sig, siginfo_t * info, void * context)
         ::sleep(10);
         call_default_signal_handler(sig);
     }
+
+    errno = saved_errno;
 }
 
 

dbms/src/Common/QueryProfiler.cpp

@@ -21,6 +21,8 @@ namespace
 {
     void writeTraceInfo(TraceType trace_type, int /* sig */, siginfo_t * info, void * context)
     {
+        auto saved_errno = errno;   /// We must restore previous value of errno in signal handler.
+
         int overrun_count = 0;
 #if defined(OS_LINUX)
         if (info)
@@ -33,6 +35,8 @@ namespace
         const StackTrace stack_trace(signal_context);
 
         ext::Singleton<TraceCollector>()->collect(trace_type, stack_trace, overrun_count);
+
+        errno = saved_errno;
     }
 
     [[maybe_unused]] const UInt32 TIMER_PRECISION = 1e9;

dbms/src/Storages/System/StorageSystemStackTrace.cpp

@@ -47,6 +47,8 @@ namespace
 
     void signalHandler(int, siginfo_t * info, void * context)
     {
+        auto saved_errno = errno;   /// We must restore previous value of errno in signal handler.
+
         /// In case malicious user is sending signals manually (for unknown reason).
         /// If we don't check - it may break our synchronization.
         if (info->si_pid != expected_pid)
@@ -69,6 +71,8 @@ namespace
 
         /// We cannot do anything if write failed.
         (void)res;
+
+        errno = saved_errno;
     }
 
     /// Wait for data in pipe and read it.