Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

# gpg: Signature made Tue 13 Jan 2015 13:48:06 GMT using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"

* remotes/stefanha/tags/block-pull-request: (38 commits)
  NVMe: Set correct VS Value for 1.1 Compliant Controllers
  MAINTAINERS: Add migration/block* to block subsystem
  MAINTAINERS: Update email addresses for Chrysostomos Nanakos
  nvme: Fix get/set number of queues feature
  ide: Implement VPD response for ATAPI
  block: Split BLOCK_OP_TYPE_COMMIT to BLOCK_OP_TYPE_COMMIT_{SOURCE, TARGET}
  block: limited request size in write zeroes unsupported path
  coroutine: try harder not to delete coroutines
  coroutine: drop qemu_coroutine_adjust_pool_size
  coroutine: rewrite pool to avoid mutex
  QSLIST: add lock-free operations
  test-coroutine: avoid overflow on 32-bit systems
  qemu-thread: add per-thread atexit functions
  coroutine-ucontext: use __thread
  qemu-iotests: Add supported os parameter for python tests
  qemu-iotests: Add "_supported_os Linux" to 058
  qemu-iotests: Replace "/bin/true" with "true"
  .gitignore: Ignore generated "common.env"
  libqos: Convert malloc-pc allocator to a generic allocator
  migration/block: fix pending() return value
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 19 insertions, 50 deletions

diff --git a/coroutine-ucontext.c b/coroutine-ucontext.c
index 4bf2cde279..259fcb48a4 100644
--- a/coroutine-ucontext.c
+++ b/coroutine-ucontext.c
@@ -25,7 +25,6 @@
 #include <stdlib.h>
 #include <setjmp.h>
 #include <stdint.h>
-#include <pthread.h>
 #include <ucontext.h>
 #include "qemu-common.h"
 #include "block/coroutine_int.h"
@@ -48,15 +47,8 @@ typedef struct {
 /**
  * Per-thread coroutine bookkeeping
  */
-typedef struct {
-    /** Currently executing coroutine */
-    Coroutine *current;
-
-    /** The default coroutine */
-    CoroutineUContext leader;
-} CoroutineThreadState;
-
-static pthread_key_t thread_state_key;
+static __thread CoroutineUContext leader;
+static __thread Coroutine *current;
 
 /*
  * va_args to makecontext() must be type 'int', so passing
@@ -68,36 +60,6 @@ union cc_arg {
     int i[2];
 };
 
-static CoroutineThreadState *coroutine_get_thread_state(void)
-{
-    CoroutineThreadState *s = pthread_getspecific(thread_state_key);
-
-    if (!s) {
-        s = g_malloc0(sizeof(*s));
-        s->current = &s->leader.base;
-        pthread_setspecific(thread_state_key, s);
-    }
-    return s;
-}
-
-static void qemu_coroutine_thread_cleanup(void *opaque)
-{
-    CoroutineThreadState *s = opaque;
-
-    g_free(s);
-}
-
-static void __attribute__((constructor)) coroutine_init(void)
-{
-    int ret;
-
-    ret = pthread_key_create(&thread_state_key, qemu_coroutine_thread_cleanup);
-    if (ret != 0) {
-        fprintf(stderr, "unable to create leader key: %s\n", strerror(errno));
-        abort();
-    }
-}
-
 static void coroutine_trampoline(int i0, int i1)
 {
     union cc_arg arg;
@@ -193,15 +155,23 @@ void qemu_coroutine_delete(Coroutine *co_)
     g_free(co);
 }
 
-CoroutineAction qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
-                                      CoroutineAction action)
+/* This function is marked noinline to prevent GCC from inlining it
+ * into coroutine_trampoline(). If we allow it to do that then it
+ * hoists the code to get the address of the TLS variable "current"
+ * out of the while() loop. This is an invalid transformation because
+ * the sigsetjmp() call may be called when running thread A but
+ * return in thread B, and so we might be in a different thread
+ * context each time round the loop.
+ */
+CoroutineAction __attribute__((noinline))
+qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
+                      CoroutineAction action)
 {
     CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_);
     CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_);
-    CoroutineThreadState *s = coroutine_get_thread_state();
     int ret;
 
-    s->current = to_;
+    current = to_;
 
     ret = sigsetjmp(from->env, 0);
     if (ret == 0) {
@@ -212,14 +182,13 @@ CoroutineAction qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
 
 Coroutine *qemu_coroutine_self(void)
 {
-    CoroutineThreadState *s = coroutine_get_thread_state();
-
-    return s->current;
+    if (!current) {
+        current = &leader.base;
+    }
+    return current;
 }
 
 bool qemu_in_coroutine(void)
 {
-    CoroutineThreadState *s = pthread_getspecific(thread_state_key);
-
-    return s && s->current->caller;
+    return current && current->caller;
 }