systemtap/systemtap_improve_gettimeofday_stability.patch

From: Josh Stone <jistone@redhat.com>
Subject: Improve gettimeofday stability
References: bnc#664105
Patch-Mainline: yes
Git-commit: 3fd1c4901e81e5f6b550bb988d612281e0fc231b
Git-repo: git://sources.redhat.com/git/systemtap.git

Signed-off-by: Thomas Renninger <trenn@suse.de>

These are a few tweaks to improve the stability of our gettimeofday
startup and shutdown.  Hopefully this helps with PR10651 and PR12182,
but that's not been confirmed yet.

* runtime/runtime.h: Don't include time.c here.
* translate.cxx (c_unparser::emit_common_header): Include time.c here,
  only if NEEDed (so we also ensure init/kill_time will be called).
  (c_unparser::emit_module_init): Change to STAP_SESSION_STOPPED for the
  final cleanup efforts, especially for time.c to wrap up.
  (c_unparser::emit_module_exit): Ditto.
* runtime/time.c (__stp_time_timer_callback): Use the session_state
  instead of stp_timer_reregister, and continue until STOPPED.
  (__stp_init_time): Don't add_timer from the IPI.
  (_stp_init_time): Instead, add_timer_on each cpu here.

diff --git a/runtime/runtime.h b/runtime/runtime.h
index d4f41db..814d8ad 100644
--- a/runtime/runtime.h
+++ b/runtime/runtime.h
@@ -132,7 +132,6 @@ static struct
 #include "copy.c"
 #include "regs.c"
 #include "regs-ia64.c"
-#include "time.c"
 
 #include "task_finder.c"
 
diff --git a/runtime/time.c b/runtime/time.c
index 0d13487..38a808a 100644
--- a/runtime/time.c
+++ b/runtime/time.c
@@ -56,9 +56,6 @@ typedef struct __stp_time_t {
 
 static void *stp_time = NULL;
 
-/* Flag to tell the timer callback whether to reregister */
-static int stp_timer_reregister = 0;
-
 /* Try to estimate the number of CPU cycles in a millisecond - i.e. kHz.  This
  * relies heavily on the accuracy of udelay.  By calling udelay twice, we
  * attempt to account for overhead in the call.
@@ -134,7 +131,7 @@ __stp_time_timer_callback(unsigned long val)
        XXX: The worst that can probably happen is that we get
 	    two consecutive timer resets.  */
 
-    if (likely(stp_timer_reregister))
+    if (likely(atomic_read(&session_state) != STAP_SESSION_STOPPED))
         mod_timer(&time->timer, jiffies + 1);
 }
 
@@ -154,7 +151,6 @@ __stp_init_time(void *info)
     init_timer(&time->timer);
     time->timer.expires = jiffies + 1;
     time->timer.function = __stp_time_timer_callback;
-    add_timer(&time->timer);
 }
 
 #ifdef CONFIG_CPU_FREQ
@@ -208,7 +204,6 @@ _stp_kill_time(void)
 {
     if (stp_time) {
         int cpu;
-        stp_timer_reregister = 0;
         for_each_online_cpu(cpu) {
             stp_time_t *time = per_cpu_ptr(stp_time, cpu);
             del_timer_sync(&time->timer);
@@ -229,20 +224,23 @@ _stp_kill_time(void)
 static int
 _stp_init_time(void)
 {
-    int ret = 0;
+    int cpu, ret = 0;
 
     _stp_kill_time();
 
     stp_time = _stp_alloc_percpu(sizeof(stp_time_t));
     if (unlikely(stp_time == 0))
 	    return -1;
-    
-    stp_timer_reregister = 1;
+
 #ifdef STAPCONF_ONEACHCPU_RETRY
     ret = on_each_cpu(__stp_init_time, NULL, 0, 1);
 #else
     ret = on_each_cpu(__stp_init_time, NULL, 1);
 #endif
+    for_each_online_cpu(cpu) {
+        stp_time_t *time = per_cpu_ptr(stp_time, cpu);
+        add_timer_on(&time->timer, cpu);
+    }
 
 #ifdef CONFIG_CPU_FREQ
     if (!ret && !__stp_constant_freq()) {
@@ -250,7 +248,6 @@ _stp_init_time(void)
                 CPUFREQ_TRANSITION_NOTIFIER);
 
         if (!ret) {
-            int cpu;
             for_each_online_cpu(cpu) {
                 unsigned long flags;
                 int freq_khz = cpufreq_get(cpu);
diff --git a/translate.cxx b/translate.cxx
index f360940..4447a24 100644
--- a/translate.cxx
+++ b/translate.cxx
@@ -1085,6 +1085,10 @@ c_unparser::emit_common_header ()
   if (!session->stat_decls.empty())
     o->newline() << "#include \"stat.c\"\n";
 
+  o->newline() << "#ifdef STAP_NEED_GETTIMEOFDAY";
+  o->newline() << "#include \"time.c\"";  // Don't we all need more?
+  o->newline() << "#endif";
+
   o->newline();
 }
 
@@ -1327,6 +1331,7 @@ c_unparser::emit_module_init ()
     }
 
   // For any partially registered/unregistered kernel facilities.
+  o->newline() << "atomic_set (&session_state, STAP_SESSION_STOPPED);";
   o->newline() << "#ifdef STAPCONF_SYNCHRONIZE_SCHED";
   o->newline() << "synchronize_sched();";
   o->newline() << "#endif";
@@ -1409,6 +1414,7 @@ c_unparser::emit_module_exit ()
   o->newline(-2) << "} while (holdon);";
 
   // cargo cult epilogue
+  o->newline() << "atomic_set (&session_state, STAP_SESSION_STOPPED);";
   o->newline() << "#ifdef STAPCONF_SYNCHRONIZE_SCHED";
   o->newline() << "synchronize_sched();";
   o->newline() << "#endif";