mnt: inform user of slow mountlist scan

This will inform the user of why cmogstored may be slow
to start, since we need the mountlist to be populated at
startup.

We also throw a pthread_cancel() in there to load libgcc_s under
glibc, so we can avoid loading libgcc_s once we're under FD pressure.
This makes test/http_idle_expire.rb more reliable.

6 files changed, 103 insertions, 10 deletions

diff --git a/Makefile.am b/Makefile.am
index 1e2b598..6fa520c 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,7 +1,7 @@
 ACLOCAL_AMFLAGS = -I m4
 AM_CPPFLAGS = -I$(top_builddir)/lib -I$(top_srcdir)/lib
 AM_CFLAGS = $(WARN_CFLAGS) $(PTHREAD_CFLAGS)
-AM_LDFLAGS = $(LIBGNU_LIBDEPS)
+AM_LDFLAGS = $(LIBGNU_LIBDEPS) $(LIB_CLOCK_GETTIME)
 SUBDIRS = lib
 
 # slow.mk is auto-generated by the maintainer (see GNUmakefile)
diff --git a/cmogstored.h b/cmogstored.h
index 2a31857..393cecb 100644
--- a/cmogstored.h
+++ b/cmogstored.h
@@ -20,6 +20,7 @@
 #include <sys/uio.h>
 #include <sys/mman.h>
 #include <sys/types.h>
+#include <sys/select.h>
 #include <sys/stat.h>
 #include <sys/socket.h>
 #include <sys/ioctl.h>
@@ -62,6 +63,7 @@
 #include "gc.h"
 #include "nproc.h"
 #include "findprog.h"
+#include "timespec.h"
 
 #include "gcc.h"
 #include "util.h"
@@ -412,6 +414,7 @@ enum mog_next mog_queue_step(struct mog_fd *mfd) MOG_CHECK;
 /* sig.c */
 void mog_intr_disable(void);
 void mog_intr_enable(void);
+void mog_sleep(long seconds);
 
 /* file.c */
 struct mog_fd * mog_file_open_read(struct mog_svc *, char *path);
diff --git a/m4/.gitignore b/m4/.gitignore
index 391f27d..a0934c7 100644
--- a/m4/.gitignore
+++ b/m4/.gitignore
@@ -175,3 +175,6 @@
 /eaccess.m4
 /findprog.m4
 /stpcpy.m4
+/clock_time.m4
+/gettime.m4
+/timespec.m4
diff --git a/m4/gnulib-cache.m4 b/m4/gnulib-cache.m4
index 1eeafec..03015fb 100644
--- a/m4/gnulib-cache.m4
+++ b/m4/gnulib-cache.m4
@@ -27,7 +27,7 @@
 
 
 # Specification in the form of a command-line invocation:
-#   gnulib-tool --import --dir=. --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --with-tests --avoid=accept --avoid=accept4 --avoid=alloca --avoid=fstatat --avoid=getcwd --avoid=ioctl --avoid=openat --avoid=read --avoid=sleep --avoid=write --no-conditional-dependencies --no-libtool --macro-prefix=gl argp base64 canonicalize crypto/gc-md5 crypto/gc-sha1 dprintf error findprog git-version-gen hash mempcpy minmax mountlist nonblocking nproc pipe2 progname random_r verify warnings xvasprintf
+#   gnulib-tool --import --dir=. --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --with-tests --avoid=accept --avoid=accept4 --avoid=alloca --avoid=fstatat --avoid=getcwd --avoid=ioctl --avoid=openat --avoid=read --avoid=sleep --avoid=write --no-conditional-dependencies --no-libtool --macro-prefix=gl argp base64 canonicalize crypto/gc-md5 crypto/gc-sha1 dprintf error findprog gettime git-version-gen hash mempcpy minmax mountlist nonblocking nproc pipe2 progname random_r verify warnings xvasprintf
 
 # Specification in the form of a few gnulib-tool.m4 macro invocations:
 gl_LOCAL_DIR([])
@@ -40,6 +40,7 @@ gl_MODULES([
   dprintf
   error
   findprog
+  gettime
   git-version-gen
   hash
   mempcpy
diff --git a/mnt.c b/mnt.c
index 8b34255..57f5e07 100644
--- a/mnt.c
+++ b/mnt.c
@@ -8,6 +8,11 @@
  */
 #include "cmogstored.h"
 
+struct init_args {
+        pthread_mutex_t cond_lock;
+        pthread_cond_t cond;
+};
+
 static pthread_mutex_t by_dev_lock = PTHREAD_MUTEX_INITIALIZER;
 
 /*
@@ -113,6 +118,73 @@ skip:
         }
 }
 
+/* runs inside a thread, this is called at startup before daemonization */
+static void * init_once(void *ptr)
+{
+        struct init_args *ia = ptr;
+
+        CHECK(int, 0, pthread_mutex_lock(&by_dev_lock) );
+        assert(by_dev == NULL &&
+               "by_dev exists during initialization");
+        by_dev = mnt_new(7);
+        mnt_populate(by_dev);
+        CHECK(int, 0, pthread_mutex_unlock(&by_dev_lock) );
+
+        /* wake up parent thread, this tells parent to cancel us */
+        CHECK(int, 0, pthread_mutex_lock(&ia->cond_lock));
+        CHECK(int, 0, pthread_cond_signal(&ia->cond));
+        CHECK(int, 0, pthread_mutex_unlock(&ia->cond_lock));
+
+        mog_sleep(-1); /* wait for cancellation */
+        assert(0 && "init_once did not get cancelled");
+        return NULL;
+}
+
+/* once-only initialization */
+static void timed_init_once(void)
+{
+        pthread_t thr;
+        unsigned long tries;
+        struct init_args ia = {
+                .cond_lock = PTHREAD_MUTEX_INITIALIZER,
+                .cond = PTHREAD_COND_INITIALIZER
+        };
+
+        CHECK(int, 0, pthread_mutex_lock(&ia.cond_lock));
+        CHECK(int, 0, pthread_create(&thr, NULL, init_once, &ia));
+
+        for (tries = 1; ; tries++) {
+                struct timespec ts;
+                int rc;
+
+                gettime(&ts);
+                ts.tv_sec += 5;
+                rc = pthread_cond_timedwait(&ia.cond, &ia.cond_lock, &ts);
+
+                if (rc == 0)
+                        break;
+                if (rc == ETIMEDOUT)
+                        warn("still populating mountlist (tries: %lu)", tries);
+                else if (rc == EINTR)
+                        continue;
+                else
+                        assert(0 && "unhandled pthread_cond_timedwait failure");
+        }
+        CHECK(int, 0, pthread_mutex_unlock(&ia.cond_lock));
+
+        /*
+         * this will load libgcc_s under glibc, we want to do this early
+         * in process lifetime to prevent load failures if we are under
+         * FD pressure later on.
+         */
+        CHECK(int, 0, pthread_cancel(thr));
+
+        CHECK(int, 0, pthread_join(thr, NULL));
+        CHECK(int, 0, pthread_cond_destroy(&ia.cond));
+        CHECK(int, 0, pthread_mutex_destroy(&ia.cond_lock));
+        atexit(mnt_atexit);
+}
+
 void mog_mnt_refresh(void)
 {
         Hash_table *new, *old;
@@ -146,14 +218,7 @@ void mog_mnt_refresh(void)
                 mog_iou_cleanup_finish();
                 hash_free(old);
         } else {
-                /* once-only initialization */
-                CHECK(int, 0, pthread_mutex_lock(&by_dev_lock) );
-                assert(by_dev == NULL &&
-                       "by_dev exists during initialization");
-                by_dev = mnt_new(7);
-                mnt_populate(by_dev);
-                CHECK(int, 0, pthread_mutex_unlock(&by_dev_lock) );
-                atexit(mnt_atexit);
+                timed_init_once();
         }
 
         CHECK(int, 0, pthread_mutex_unlock(&refresh_lock) );
diff --git a/sig.c b/sig.c
index 63a40fe..7fa2708 100644
--- a/sig.c
+++ b/sig.c
@@ -23,3 +23,24 @@ void mog_intr_enable(void)
         CHECK(int, 0, sigemptyset(&set));
         CHECK(int, 0, pthread_sigmask(SIG_SETMASK, &set, NULL));
 }
+
+/* thread-safe, interruptible sleep, negative seconds -> sleep forever */
+void mog_sleep(long seconds)
+{
+        sigset_t set;
+        struct timespec ts;
+        struct timespec *tsp;
+
+        if (seconds < 0) {
+                tsp = NULL;
+        } else {
+                ts.tv_sec = seconds;
+                ts.tv_nsec = 0;
+                tsp = &ts;
+        }
+
+        CHECK(int, 0, sigemptyset(&set));
+        if (pselect(0, NULL, NULL, NULL, tsp, &set) < 0)
+                assert((errno == EINTR || errno == ENOMEM) &&
+                       "BUG in pselect usage");
+}