Revert "epoll: avoid EPOLL_CTL_MOD race condition"

This reverts commit 02e5a91b24983d96b342c007661966495ccdb619.

This workaround may have unintended side-effects for apps using
EPOLL_CTL_DEL.

3 files changed, 14 insertions, 118 deletions

diff --git a/ext/sleepy_penguin/epoll.c b/ext/sleepy_penguin/epoll.c
index 60a34be..a507b0c 100644
--- a/ext/sleepy_penguin/epoll.c
+++ b/ext/sleepy_penguin/epoll.c
@@ -2,9 +2,6 @@
 #include <sys/epoll.h>
 #include <pthread.h>
 #include <time.h>
-#include <stdio.h>
-#include <unistd.h>
-#include <sys/utsname.h>
 #include "missing_epoll.h"
 #ifdef HAVE_RUBY_ST_H
 #  include <ruby/st.h>
@@ -198,75 +195,6 @@ static VALUE init(int argc, VALUE *argv, VALUE self)
         return self;
 }
 
-static int epoll_ctl_mod_racy;
-static void epoll_ctl_mod_racy_detect(void)
-{
-        struct utsname buf;
-        int rc;
-        unsigned version, patchlevel, sublevel;
-
-        /*
-         * Online/current processors for this process is not enough,
-         * we need all processors since events may be triggered
-         * by interrupt handlers on any CPU in the system
-         */
-        long nproc = sysconf(_SC_NPROCESSORS_CONF);
-
-        /* Eric Wong's personal machines are ancient and weak: */
-        if (nproc == 1)
-                return;
-
-        if (uname(&buf) != 0)
-                rb_sys_fail("uname");
-
-        /* who knows, maybe there'll be an epoll on other OSes one day */
-        if (strcmp(buf.sysname, "Linux"))
-                return;
-
-        rc = sscanf(buf.release, "%u.%u.%u", &version, &patchlevel, &sublevel);
-        if (rc != 3) {
-                rb_warn("sscanf failed to parse kernel version: %s (rc=%d), "
-                        "assuming EPOLL_CTL_MOD is racy on SMP",
-                        buf.release, rc);
-                epoll_ctl_mod_racy = 1;
-                return;
-        }
-
-        /*
-         * TODO: whitelist vendor kernels as fixes are backported
-         * TODO: It is likely 3.7.2 (or 3.7.3) will have this
-         *       fix backported.
-         */
-        if (version <= 2) {
-                epoll_ctl_mod_racy = 1;
-        } else if (version == 3) {
-                if (patchlevel <= 7)
-                        epoll_ctl_mod_racy = 1;
-        }
-}
-
-/*
- * EPOLL_CTL_MOD is racy under Linux <= 3.7.1 on SMP systems,
- * so we emulate it with EPOLL_CTL_ADD + EPOLL_CTL_DELETE
- * This is fixed in Linux commit 128dd1759d96ad36c379240f8b9463e8acfd37a1
- */
-static int
-fake_epoll_ctl_mod(int epfd, int fd, struct epoll_event *event)
-{
-        int rc = epoll_ctl(epfd, EPOLL_CTL_DEL, fd, event);
-        if (rc == 0)
-                rc = epoll_ctl(epfd, EPOLL_CTL_ADD, fd, event);
-        return rc;
-}
-
-static int my_epoll_ctl(int epfd, int op, int fd, struct epoll_event *event)
-{
-        if (epoll_ctl_mod_racy && op == EPOLL_CTL_MOD)
-                return fake_epoll_ctl_mod(epfd, fd, event);
-        else
-                return epoll_ctl(epfd, op, fd, event);
-}
-
 static VALUE ctl(VALUE self, VALUE io, VALUE flags, int op)
 {
         struct epoll_event event;
@@ -278,11 +206,11 @@ static VALUE ctl(VALUE self, VALUE io, VALUE flags, int op)
         event.events = rb_sp_get_uflags(self, flags);
         pack_event_data(&event, io);
 
-        rv = my_epoll_ctl(ep->fd, op, fd, &event);
+        rv = epoll_ctl(ep->fd, op, fd, &event);
         if (rv == -1) {
                 if (errno == ENOMEM) {
                         rb_gc();
-                        rv = my_epoll_ctl(ep->fd, op, fd, &event);
+                        rv = epoll_ctl(ep->fd, op, fd, &event);
                 }
                 if (rv == -1)
                         rb_sys_fail("epoll_ctl");
@@ -341,7 +269,7 @@ static VALUE set(VALUE self, VALUE io, VALUE flags)
                         return Qnil;
 
 fallback_mod:
-                rv = my_epoll_ctl(ep->fd, EPOLL_CTL_MOD, fd, &event);
+                rv = epoll_ctl(ep->fd, EPOLL_CTL_MOD, fd, &event);
                 if (rv == -1) {
                         if (errno != ENOENT)
                                 rb_sys_fail("epoll_ctl - mod");
@@ -858,16 +786,4 @@ void sleepy_penguin_init_epoll(void)
         rb_define_const(cEpoll, "ONESHOT", UINT2NUM(EPOLLONESHOT));
 
         id_for_fd = rb_intern("for_fd");
-
-        epoll_ctl_mod_racy_detect();
-
-
-        /*
-         * true if EPOLL_CTL_MOD is racy on your version of Linux
-         * (anything before 3.8) under SMP.
-         * Please report patched vendor kernels to
-         * mailto:sleepy.penguin@librelist.org
-         */
-        rb_define_const(cEpoll, "EPOLL_CTL_MOD_RACY",
-                        epoll_ctl_mod_racy ? Qtrue : Qfalse);
 }
diff --git a/test/test_epoll.rb b/test/test_epoll.rb
index 1eb987e..fd22654 100644
--- a/test/test_epoll.rb
+++ b/test/test_epoll.rb
@@ -18,10 +18,7 @@ class TestEpoll < Test::Unit::TestCase
 
   def test_constants
     Epoll.constants.each do |const|
-      case const.to_sym
-      when :IO, :EPOLL_CTL_MOD_RACY
-        next
-      end
+      next if const.to_sym == :IO
       nr = Epoll.const_get(const)
       assert nr <= 0xffffffff, "#{const}=#{nr}"
     end
diff --git a/test/test_epoll_optimizations.rb b/test/test_epoll_optimizations.rb
index cdb94c8..bd77397 100644
--- a/test/test_epoll_optimizations.rb
+++ b/test/test_epoll_optimizations.rb
@@ -31,34 +31,17 @@ class TestEpollOptimizations < Test::Unit::TestCase
     assert_equal 1, lines.grep(/^epoll_ctl/).size
     assert_match(/EPOLL_CTL_ADD/, lines.grep(/^epoll_ctl/)[0])
 
-    if Epoll::EPOLL_CTL_MOD_RACY
-      io, err = Strace.me { @ep.set(@wr, Epoll::OUT | Epoll::ONESHOT) }
-      assert_nil err
-      lines = io.readlines; io.close
-      assert_equal 2, lines.grep(/^epoll_ctl/).size
-      assert_match(/EPOLL_CTL_DEL/, lines.grep(/^epoll_ctl/)[0])
-      assert_match(/EPOLL_CTL_ADD/, lines.grep(/^epoll_ctl/)[1])
-
-      io, err = Strace.me { @ep.set(@wr, Epoll::OUT) }
-      assert_nil err
-      lines = io.readlines; io.close
-      assert_equal 2, lines.grep(/^epoll_ctl/).size
-      assert_match(/EPOLL_CTL_DEL/, lines.grep(/^epoll_ctl/)[0])
-      assert_match(/EPOLL_CTL_ADD/, lines.grep(/^epoll_ctl/)[1])
-    else
-      io, err = Strace.me { @ep.set(@wr, Epoll::OUT | Epoll::ONESHOT) }
-      assert_nil err
-      lines = io.readlines; io.close
-      assert_equal 1, lines.grep(/^epoll_ctl/).size
-      assert_match(/EPOLL_CTL_MOD/, lines.grep(/^epoll_ctl/)[0])
-
-      io, err = Strace.me { @ep.set(@wr, Epoll::OUT) }
-      assert_nil err
-      lines = io.readlines; io.close
-      assert_equal 1, lines.grep(/^epoll_ctl/).size
-      assert_match(/EPOLL_CTL_MOD/, lines.grep(/^epoll_ctl/)[0])
-    end
+    io, err = Strace.me { @ep.set(@wr, Epoll::OUT | Epoll::ONESHOT) }
+    assert_nil err
+    lines = io.readlines; io.close
+    assert_equal 1, lines.grep(/^epoll_ctl/).size
+    assert_match(/EPOLL_CTL_MOD/, lines.grep(/^epoll_ctl/)[0])
 
+    io, err = Strace.me { @ep.set(@wr, Epoll::OUT) }
+    assert_nil err
+    lines = io.readlines; io.close
+    assert_equal 1, lines.grep(/^epoll_ctl/).size
+    assert_match(/EPOLL_CTL_MOD/, lines.grep(/^epoll_ctl/)[0])
     @wr.close
     @rd.close