Blame SOURCES/kvm-Init-the-XBZRLE.lock-in-ram_mig_init.patch

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From ac978ade92aa12ae6c700b8be85a10355f728c78 Mon Sep 17 00:00:00 2001
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From: Dr. David Alan Gilbert (git) <dgilbert@redhat.com>
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Date: Thu, 8 May 2014 10:58:41 +0200
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Subject: [PATCH 19/30] Init the XBZRLE.lock in ram_mig_init
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RH-Author: Dr. David Alan Gilbert (git) <dgilbert@redhat.com>
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Message-id: <1399546722-6350-4-git-send-email-dgilbert@redhat.com>
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Patchwork-id: 58743
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O-Subject: [RHEL7.1/RHEL7.0.z qemu-kvm PATCH 3/4] Init the XBZRLE.lock in ram_mig_init
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Bugzilla: 1110191
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RH-Acked-by: Juan Quintela <quintela@redhat.com>
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RH-Acked-by: Markus Armbruster <armbru@redhat.com>
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RH-Acked-by: Amit Shah <amit.shah@redhat.com>
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From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
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Initialising the XBZRLE.lock earlier simplifies the lock use.
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Based on Markus's patch in:
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http://lists.gnu.org/archive/html/qemu-devel/2014-03/msg03879.html
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Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Reviewed-by: Gonglei <arei.gonglei@huawei.com>
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Reviewed-by: Markus Armbruster <armbru@redhat.com>
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Signed-off-by: Juan Quintela <quintela@redhat.com>
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(cherry picked from commit d97326eec2ca1313eaf0b5cffd69af5663b5af5d)
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---
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 arch_init.c | 61 +++++++++++++++++++++++++++++++------------------------------
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 1 file changed, 31 insertions(+), 30 deletions(-)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 arch_init.c |   61 ++++++++++++++++++++++++++++++-----------------------------
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 1 files changed, 31 insertions(+), 30 deletions(-)
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diff --git a/arch_init.c b/arch_init.c
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index 37c9f6d..80e48f2 100644
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--- a/arch_init.c
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+++ b/arch_init.c
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@@ -45,6 +45,7 @@
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 #include "hw/audio/pcspk.h"
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 #include "migration/page_cache.h"
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 #include "qemu/config-file.h"
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+#include "qemu/error-report.h"
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 #include "qmp-commands.h"
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 #include "trace.h"
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 #include "exec/cpu-all.h"
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@@ -167,11 +168,8 @@ static struct {
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     /* Cache for XBZRLE, Protected by lock. */
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     PageCache *cache;
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     QemuMutex lock;
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-} XBZRLE = {
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-    .encoded_buf = NULL,
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-    .current_buf = NULL,
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-    .cache = NULL,
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-};
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+} XBZRLE;
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+
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 /* buffer used for XBZRLE decoding */
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 static uint8_t *xbzrle_decoded_buf;
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@@ -187,41 +185,44 @@ static void XBZRLE_cache_unlock(void)
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         qemu_mutex_unlock(&XBZRLE.lock);
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 }
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+/*
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+ * called from qmp_migrate_set_cache_size in main thread, possibly while
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+ * a migration is in progress.
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+ * A running migration maybe using the cache and might finish during this
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+ * call, hence changes to the cache are protected by XBZRLE.lock().
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+ */
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 int64_t xbzrle_cache_resize(int64_t new_size)
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 {
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-    PageCache *new_cache, *cache_to_free;
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+    PageCache *new_cache;
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+    int64_t ret;
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     if (new_size < TARGET_PAGE_SIZE) {
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         return -1;
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     }
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-    /* no need to lock, the current thread holds qemu big lock */
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+    XBZRLE_cache_lock();
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+
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     if (XBZRLE.cache != NULL) {
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-        /* check XBZRLE.cache again later */
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         if (pow2floor(new_size) == migrate_xbzrle_cache_size()) {
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-            return pow2floor(new_size);
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+            goto out_new_size;
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         }
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         new_cache = cache_init(new_size / TARGET_PAGE_SIZE,
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                                         TARGET_PAGE_SIZE);
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         if (!new_cache) {
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-            DPRINTF("Error creating cache\n");
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-            return -1;
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-        }
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-
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-        XBZRLE_cache_lock();
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-        /* the XBZRLE.cache may have be destroyed, check it again */
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-        if (XBZRLE.cache != NULL) {
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-            cache_to_free = XBZRLE.cache;
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-            XBZRLE.cache = new_cache;
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-        } else {
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-            cache_to_free = new_cache;
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+            error_report("Error creating cache");
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+            ret = -1;
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+            goto out;
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         }
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-        XBZRLE_cache_unlock();
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-        cache_fini(cache_to_free);
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+        cache_fini(XBZRLE.cache);
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+        XBZRLE.cache = new_cache;
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     }
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-    return pow2floor(new_size);
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+out_new_size:
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+    ret = pow2floor(new_size);
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+out:
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+    XBZRLE_cache_unlock();
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+    return ret;
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 }
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 /* accounting for migration statistics */
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@@ -735,28 +736,27 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
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     dirty_rate_high_cnt = 0;
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     if (migrate_use_xbzrle()) {
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-        qemu_mutex_lock_iothread();
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+        XBZRLE_cache_lock();
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         XBZRLE.cache = cache_init(migrate_xbzrle_cache_size() /
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                                   TARGET_PAGE_SIZE,
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                                   TARGET_PAGE_SIZE);
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         if (!XBZRLE.cache) {
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-            qemu_mutex_unlock_iothread();
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-            DPRINTF("Error creating cache\n");
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+            XBZRLE_cache_unlock();
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+            error_report("Error creating cache");
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             return -1;
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         }
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-        qemu_mutex_init(&XBZRLE.lock);
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-        qemu_mutex_unlock_iothread();
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+        XBZRLE_cache_unlock();
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         /* We prefer not to abort if there is no memory */
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         XBZRLE.encoded_buf = g_try_malloc0(TARGET_PAGE_SIZE);
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         if (!XBZRLE.encoded_buf) {
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-            DPRINTF("Error allocating encoded_buf\n");
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+            error_report("Error allocating encoded_buf");
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             return -1;
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         }
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         XBZRLE.current_buf = g_try_malloc(TARGET_PAGE_SIZE);
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         if (!XBZRLE.current_buf) {
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-            DPRINTF("Error allocating current_buf\n");
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+            error_report("Error allocating current_buf");
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             g_free(XBZRLE.encoded_buf);
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             XBZRLE.encoded_buf = NULL;
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             return -1;
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@@ -1110,6 +1110,7 @@ static SaveVMHandlers savevm_ram_handlers = {
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 void ram_mig_init(void)
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 {
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+    qemu_mutex_init(&XBZRLE.lock);
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     register_savevm_live(NULL, "ram", 0, 4, &savevm_ram_handlers, NULL);
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 }
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-- 
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1.7.1
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