Merge pull request #439 from whitslack/oom-score-adj

distccd: add --oom-score-adj option (Linux only)

6 files changed, 54 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 948946b..4d709e0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -15,6 +15,18 @@ AC_INIT(distcc, 3.4, distcc@lists.samba.org)
 AC_CONFIG_HEADERS(src/config.h)
 AC_CONFIG_MACRO_DIRS([m4])
 
+AC_CANONICAL_HOST
+AC_MSG_CHECKING([if the host system type is Linux])
+case "${host_os}" in
+linux*)
+	AC_MSG_RESULT(yes)
+	AC_DEFINE(HAVE_LINUX, 1, [Define to 1 if the host system type is Linux.])
+	;;
+*)
+	AC_MSG_RESULT(no)
+	;;
+esac
+
 # FreeBSD installs its version of libpopt into /usr/local/, but does
 # not put that on the default library and header path.
 # Solaris doesn't even ship libpopt.  We used to add that path if
diff --git a/man/distccd.1 b/man/distccd.1
index 4ff4e44..9cf8d1c 100644
--- a/man/distccd.1
+++ b/man/distccd.1
@@ -123,6 +123,13 @@ the machine.  NICENESS is an increment to the current priority of the
 process.  The range of priorities depends on the operating system but
 is typically 0 to 20.  By default the niceness is increased by 5.
 .TP
+.B --oom-score-adj ADJ
+Alters the kernel's out-of-memory killer score adjustment on worker
+processes.  ADJ is an integer ranging from -1000 to 1000, with greater
+values indicating a greater preference for killing these processes in an
+out-of-memory scenario.  By default the score adjustment is inherited
+from the process that started the distccd daemon.  (Linux only.)
+.TP
 .B -p, --port PORT
 Set the TCP port to listen on, rather than the default of 3632.
 (Daemon mode only.)
diff --git a/src/dopt.c b/src/dopt.c
index d680ad5..1e92071 100644
--- a/src/dopt.c
+++ b/src/dopt.c
@@ -33,6 +33,7 @@
 #include <fcntl.h>
 #include <errno.h>
 #include <popt.h>
+#include <limits.h>
 
 #include <sys/socket.h>
 #include <netinet/in.h>
@@ -49,6 +50,10 @@
 
 int opt_niceness = 5;           /* default */
 
+#ifdef HAVE_LINUX
+int opt_oom_score_adj = INT_MIN; /* default is not to change */
+#endif
+
 /**
  * Number of children running jobs on this machine.  If zero (recommended),
  * then dynamically set from the number of CPUs.
@@ -154,6 +159,9 @@ const struct poptOption options[] = {
     { "no-detach", 0,    POPT_ARG_NONE, &opt_no_detach, 0, 0, 0 },
     { "no-fifo", 0,      POPT_ARG_NONE, &opt_no_fifo, 0, 0, 0 },
     { "no-fork", 0,      POPT_ARG_NONE, &opt_no_fork, 0, 0, 0 },
+#ifdef HAVE_LINUX
+    { "oom-score-adj",0, POPT_ARG_INT,  &opt_oom_score_adj, 0, 0, 0 },
+#endif
     { "pid-file", 'P',   POPT_ARG_STRING, &arg_pid_file, 0, 0, 0 },
     { "port", 'p',       POPT_ARG_INT, &arg_port, 0, 0, 0 },
 #ifdef HAVE_GSSAPI
@@ -191,6 +199,9 @@ static void distccd_show_usage(void)
 #endif
 "    -P, --pid-file FILE        save daemon process id to file\n"
 "    -N, --nice LEVEL           lower priority, 20=most nice\n"
+#ifdef HAVE_LINUX
+"    --oom-score-adj ADJ        set OOM score adjustment, -1000 to 1000\n"
+#endif
 "    --user USER                if run by root, change to this persona\n"
 "    --jobs, -j LIMIT           maximum tasks at any time\n"
 "    --job-lifetime SECONDS     maximum lifetime of a compile request\n"
diff --git a/src/dopt.h b/src/dopt.h
index 70db3ca..139167b 100644
--- a/src/dopt.h
+++ b/src/dopt.h
@@ -46,6 +46,10 @@ extern int opt_lifetime;
 extern char *opt_listen_addr;
 extern int opt_niceness;
 
+#ifdef HAVE_LINUX
+extern int opt_oom_score_adj;
+#endif
+
 #ifdef HAVE_AVAHI
 extern int opt_zeroconf;
 #endif
diff --git a/src/prefork.c b/src/prefork.c
index d7e1d84..d4d70d5 100644
--- a/src/prefork.c
+++ b/src/prefork.c
@@ -38,6 +38,7 @@
 #include <signal.h>
 #include <fcntl.h>
 #include <time.h>
+#include <limits.h>
 
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -149,6 +150,16 @@ static int dcc_preforked_child(int listen_fd)
     const time_t child_lifetime = 60 /* seconds */;
     start = now = time(NULL);
 
+#ifdef HAVE_LINUX
+    if (opt_oom_score_adj != INT_MIN) {
+        FILE *f = fopen("/proc/self/oom_score_adj", "w");
+        if (!f || fprintf(f, "%d\n", opt_oom_score_adj) < 0)
+            rs_log_warning("failed to set oom_score_adj: %s", strerror(errno));
+        if (f)
+            fclose(f);
+    }
+#endif
+
     for (ireq = 0; ireq < child_requests || now - start < child_lifetime; ireq++) {
         int acc_fd;
         struct dcc_sockaddr_storage cli_addr;
diff --git a/src/setuid.c b/src/setuid.c
index d664b84..44bc850 100644
--- a/src/setuid.c
+++ b/src/setuid.c
@@ -139,6 +139,15 @@ int dcc_discard_root(void)
         return EXIT_SETUID_FAILED;
     }
 
+#ifdef HAVE_LINUX
+    /* On Linux changing the effective user or group ID clears the process's
+     * "dumpable" flag, which makes all files in the /proc/self/ directory
+     * owned by root and therefore unmodifiable by the process itself.
+     * Set the flag again here so we can, e.g., change oom_score_adj. */
+    if (prctl(PR_SET_DUMPABLE, 1, 0, 0, 0) < 0)
+        rs_log_warning("failed to restore dumpable process flag: %s", strerror(errno));
+#endif
+
 #ifdef __linux__
     if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == 0)
         rs_trace("successfully set no_new_privs");