[Qemu-devel] [PATCH 05/27] protect the ramlist with a separate mutex

[Juan Quintela <quintela@redhat.com>]

From: Umesh Deshpande <udeshpan@redhat.com>

Add the new mutex that protects shared state between ram_save_live
and the iothread.  If the iothread mutex has to be taken together
with the ramlist mutex, the iothread shall always be _outside_.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Umesh Deshpande <udeshpan@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 arch_init.c |   10 +++++++++-
 cpu-all.h   |    9 +++++++++
 exec.c      |   23 +++++++++++++++++++++--
 3 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 9e05aae..5a97710 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -492,7 +492,6 @@ static void ram_migration_cancel(void *opaque)
     migration_end();
 }

-
 static void reset_ram_globals(void)
 {
     last_block = NULL;
@@ -508,6 +507,8 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
     ram_addr_t addr;
     RAMBlock *block;

+    qemu_mutex_lock_ramlist();
+
     bytes_transferred = 0;
     reset_ram_globals();

@@ -543,6 +544,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
         qemu_put_be64(f, block->length);
     }

+    qemu_mutex_unlock_ramlist();
     qemu_put_be64(f, RAM_SAVE_FLAG_EOS);

     return 0;
@@ -556,6 +558,8 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
     int i;
     uint64_t expected_time;

+    qemu_mutex_lock_ramlist();
+
     if (ram_list.version != last_version) {
         reset_ram_globals();
     }
@@ -603,6 +607,7 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
         bwidth = 0.000001;
     }

+    qemu_mutex_unlock_ramlist();
     qemu_put_be64(f, RAM_SAVE_FLAG_EOS);

     expected_time = ram_save_remaining() * TARGET_PAGE_SIZE / bwidth;
@@ -623,6 +628,8 @@ static int ram_save_complete(QEMUFile *f, void *opaque)
 {
     memory_global_sync_dirty_bitmap(get_system_memory());

+    qemu_mutex_lock_ramlist();
+
     /* try transferring iterative blocks of memory */

     /* flush all remaining blocks regardless of rate limiting */
@@ -638,6 +645,7 @@ static int ram_save_complete(QEMUFile *f, void *opaque)
     }
     memory_global_dirty_log_stop();

+    qemu_mutex_unlock_ramlist();
     qemu_put_be64(f, RAM_SAVE_FLAG_EOS);

     return 0;
diff --git a/cpu-all.h b/cpu-all.h
index 429b2c6..0ff452f 100644
--- a/cpu-all.h
+++ b/cpu-all.h
@@ -22,6 +22,7 @@
 #include "qemu-common.h"
 #include "qemu-tls.h"
 #include "cpu-common.h"
+#include "qemu-thread.h"

 /* some important defines:
  *
@@ -476,7 +477,9 @@ typedef struct RAMBlock {
     ram_addr_t offset;
     ram_addr_t length;
     uint32_t flags;
+    /* Protected by the iothread lock.  */
     QLIST_ENTRY(RAMBlock) next_mru;
+    /* Protected by the ramlist lock.  */
     QLIST_ENTRY(RAMBlock) next;
     char idstr[256];
 #if defined(__linux__) && !defined(TARGET_S390X)
@@ -485,9 +488,12 @@ typedef struct RAMBlock {
 } RAMBlock;

 typedef struct RAMList {
+    QemuMutex mutex;
+    /* Protected by the iothread lock.  */
     uint8_t *phys_dirty;
     uint32_t version;
     QLIST_HEAD(, RAMBlock) blocks_mru;
+    /* Protected by the ramlist lock.  */
     QLIST_HEAD(, RAMBlock) blocks;
     uint64_t dirty_pages;
 } RAMList;
@@ -509,6 +515,9 @@ extern int mem_prealloc;
 void dump_exec_info(FILE *f, fprintf_function cpu_fprintf);
 #endif /* !CONFIG_USER_ONLY */

+void qemu_mutex_lock_ramlist(void);
+void qemu_mutex_unlock_ramlist(void);
+
 int cpu_memory_rw_debug(CPUArchState *env, target_ulong addr,
                         uint8_t *buf, int len, int is_write);

diff --git a/exec.c b/exec.c
index ceffa4f..53da253 100644
--- a/exec.c
+++ b/exec.c
@@ -637,6 +637,7 @@ bool tcg_enabled(void)

 void cpu_exec_init_all(void)
 {
+    qemu_mutex_init(&ram_list.mutex);
 #if !defined(CONFIG_USER_ONLY)
     memory_map_init();
     io_mem_init();
@@ -2367,6 +2368,16 @@ static long gethugepagesize(const char *path)
     return fs.f_bsize;
 }

+void qemu_mutex_lock_ramlist(void)
+{
+    qemu_mutex_lock(&ram_list.mutex);
+}
+
+void qemu_mutex_unlock_ramlist(void)
+{
+    qemu_mutex_unlock(&ram_list.mutex);
+}
+
 static void *file_ram_alloc(RAMBlock *block,
                             ram_addr_t memory,
                             const char *path)
@@ -2504,6 +2515,7 @@ void qemu_ram_set_idstr(ram_addr_t addr, const char *name, DeviceState *dev)
     }
     pstrcat(new_block->idstr, sizeof(new_block->idstr), name);

+    qemu_mutex_lock_ramlist();
     QLIST_FOREACH(block, &ram_list.blocks, next) {
         if (block != new_block && !strcmp(block->idstr, new_block->idstr)) {
             fprintf(stderr, "RAMBlock \"%s\" already registered, abort!\n",
@@ -2511,6 +2523,7 @@ void qemu_ram_set_idstr(ram_addr_t addr, const char *name, DeviceState *dev)
             abort();
         }
     }
+    qemu_mutex_unlock_ramlist();
 }

 ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
@@ -2521,6 +2534,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
     size = TARGET_PAGE_ALIGN(size);
     new_block = g_malloc0(sizeof(*new_block));

+    qemu_mutex_lock_ramlist();
     new_block->mr = mr;
     new_block->offset = find_ram_offset(size);
     if (host) {
@@ -2556,6 +2570,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
     QLIST_INSERT_HEAD(&ram_list.blocks_mru, new_block, next_mru);

     ram_list.version++;
+    qemu_mutex_unlock_ramlist();

     ram_list.phys_dirty = g_realloc(ram_list.phys_dirty,
                                        last_ram_offset() >> TARGET_PAGE_BITS);
@@ -2576,21 +2591,24 @@ void qemu_ram_free_from_ptr(ram_addr_t addr)
 {
     RAMBlock *block;

+    qemu_mutex_lock_ramlist();
     QLIST_FOREACH(block, &ram_list.blocks, next) {
         if (addr == block->offset) {
             QLIST_REMOVE(block, next);
             QLIST_REMOVE(block, next_mru);
             ram_list.version++;
             g_free(block);
-            return;
+            break;
         }
     }
+    qemu_mutex_unlock_ramlist();
 }

 void qemu_ram_free(ram_addr_t addr)
 {
     RAMBlock *block;

+    qemu_mutex_lock_ramlist();
     QLIST_FOREACH(block, &ram_list.blocks, next) {
         if (addr == block->offset) {
             QLIST_REMOVE(block, next);
@@ -2621,9 +2639,10 @@ void qemu_ram_free(ram_addr_t addr)
 #endif
             }
             g_free(block);
-            return;
+            break;
         }
     }
+    qemu_mutex_unlock_ramlist();

 }

-- 
1.7.10.4