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Blame SOURCES/kvm-migration-Make-sure-that-we-don-t-call-write-in-case.patch

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From 71b05ab5782aa1e38c016be6264a14f5650d2a87 Mon Sep 17 00:00:00 2001
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From: Juan Quintela <quintela@redhat.com>
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Date: Tue, 3 Mar 2020 14:51:35 +0000
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Subject: [PATCH 03/18] migration: Make sure that we don't call write() in case
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 of error
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RH-Author: Juan Quintela <quintela@redhat.com>
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Message-id: <20200303145143.149290-3-quintela@redhat.com>
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Patchwork-id: 94113
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O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH v2 02/10] migration: Make sure that we don't call write() in case of error
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Bugzilla: 1738451
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RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
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RH-Acked-by: Peter Xu <peterx@redhat.com>
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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If we are exiting due to an error/finish/.... Just don't try to even
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touch the channel with one IO operation.
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Signed-off-by: Juan Quintela <quintela@redhat.com>
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Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Signed-off-by: Juan Quintela <quintela@redhat.com>
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(cherry picked from commit 4d65a6216bfc44891ac298b74a6921d479805131)
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 migration/ram.c | 25 +++++++++++++++++++++++++
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 1 file changed, 25 insertions(+)
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diff --git a/migration/ram.c b/migration/ram.c
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index 65580e3..8c783b3 100644
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--- a/migration/ram.c
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+++ b/migration/ram.c
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@@ -899,6 +899,12 @@ struct {
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     uint64_t packet_num;
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     /* send channels ready */
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     QemuSemaphore channels_ready;
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+    /*
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+     * Have we already run terminate threads.  There is a race when it
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+     * happens that we got one error while we are exiting.
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+     * We will use atomic operations.  Only valid values are 0 and 1.
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+     */
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+    int exiting;
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 } *multifd_send_state;
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 /*
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@@ -927,6 +933,10 @@ static int multifd_send_pages(RAMState *rs)
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     MultiFDPages_t *pages = multifd_send_state->pages;
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     uint64_t transferred;
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+    if (atomic_read(&multifd_send_state->exiting)) {
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+        return -1;
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+    }
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+
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     qemu_sem_wait(&multifd_send_state->channels_ready);
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     for (i = next_channel;; i = (i + 1) % migrate_multifd_channels()) {
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         p = &multifd_send_state->params[i];
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@@ -1008,6 +1018,16 @@ static void multifd_send_terminate_threads(Error *err)
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         }
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     }
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+    /*
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+     * We don't want to exit each threads twice.  Depending on where
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+     * we get the error, or if there are two independent errors in two
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+     * threads at the same time, we can end calling this function
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+     * twice.
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+     */
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+    if (atomic_xchg(&multifd_send_state->exiting, 1)) {
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+        return;
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+    }
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+
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     for (i = 0; i < migrate_multifd_channels(); i++) {
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         MultiFDSendParams *p = &multifd_send_state->params[i];
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@@ -1117,6 +1137,10 @@ static void *multifd_send_thread(void *opaque)
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     while (true) {
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         qemu_sem_wait(&p->sem);
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+
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+        if (atomic_read(&multifd_send_state->exiting)) {
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+            break;
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+        }
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         qemu_mutex_lock(&p->mutex);
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         if (p->pending_job) {
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@@ -1225,6 +1249,7 @@ int multifd_save_setup(void)
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     multifd_send_state->params = g_new0(MultiFDSendParams, thread_count);
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     multifd_send_state->pages = multifd_pages_init(page_count);
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     qemu_sem_init(&multifd_send_state->channels_ready, 0);
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+    atomic_set(&multifd_send_state->exiting, 0);
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     for (i = 0; i < thread_count; i++) {
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         MultiFDSendParams *p = &multifd_send_state->params[i];
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-- 
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1.8.3.1
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