From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49908) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fVZjP-0005gG-Ol for qemu-devel@nongnu.org; Wed, 20 Jun 2018 05:48:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fVZjO-0007sY-Ov for qemu-devel@nongnu.org; Wed, 20 Jun 2018 05:48:51 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:48184 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fVZjO-0007rj-I4 for qemu-devel@nongnu.org; Wed, 20 Jun 2018 05:48:50 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 12E904022909 for ; Wed, 20 Jun 2018 09:48:50 +0000 (UTC) From: Juan Quintela In-Reply-To: <20180620094626.GD2549@work-vm> (David Alan Gilbert's message of "Wed, 20 Jun 2018 10:46:27 +0100") References: <20180523111817.1463-1-quintela@redhat.com> <20180523111817.1463-12-quintela@redhat.com> <20180611164516.GI2661@work-vm> <87d0wlyle1.fsf@secure.mitica> <20180620090127.GB2549@work-vm> <87r2l1lrp0.fsf@secure.mitica> <20180620094626.GD2549@work-vm> Reply-To: quintela@redhat.com Date: Wed, 20 Jun 2018 11:48:45 +0200 Message-ID: <87in6dlreq.fsf@secure.mitica> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH v13 11/12] migration: Remove not needed semaphore and quit List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: qemu-devel@nongnu.org, lvivier@redhat.com, peterx@redhat.com "Dr. David Alan Gilbert" wrote: > * Juan Quintela (quintela@redhat.com) wrote: >> "Dr. David Alan Gilbert" wrote: >> > * Juan Quintela (quintela@redhat.com) wrote: >> >> "Dr. David Alan Gilbert" wrote: >> >> > * Juan Quintela (quintela@redhat.com) wrote: >> >> >> We know quit closing the QIO. ... >> > Two questions from that then: >> > a) Are you sure it's safe to close the qio_channel while another >> > thread is in qio_channel_read_all_eof? Is it really defined that it >> > causes the other thread to exit with an error; close() in some stuff >> > frees data structures that the other thread is still reading; that's >> > why I've used shutdown(2) in the past rather than close on fd's >> >> Dunno if it is safe (I think it is), but I agree that shutdown will also >> get what I need. >> >> > b) I don't think your answer explains why it's an object_unref? >> >> That is the standard way to closing qios to not have to take into >> account who have it oppened. See previous paragraph, it is better to >> use shutdown, done. > > OK, great; I suspect it's unsafe because as soon as you do the unref > it could free the object; actually you should have a ref from each of > the threads to sotp it being freed while they use it. > > Dave > >> Thanks, Juan. >> >> > Dave >> > >> >> Later, Juan. >> > -- >> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK What do you think about this, to avoid me resend the whole series? >>From e03d77de1ca179fa0168cead7c23cfeae57f1787 Mon Sep 17 00:00:00 2001 From: Juan Quintela Date: Wed, 18 Apr 2018 00:49:19 +0200 Subject: [PATCH 17/18] migration: Remove not needed semaphore and quit We know quit with shutdwon in the QIO. Signed-off-by: Juan Quintela -- Add comment Use shutdown() instead of unref() --- migration/ram.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/migration/ram.c b/migration/ram.c index 2c3a452a7d..be5d26f4cb 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -594,14 +594,10 @@ typedef struct { QemuThread thread; /* communication channel */ QIOChannel *c; - /* sem where to wait for more work */ - QemuSemaphore sem; /* this mutex protects the following parameters */ QemuMutex mutex; /* is this channel thread running */ bool running; - /* should this thread finish */ - bool quit; /* array of pages to receive */ MultiFDPages_t *pages; /* packet allocated len */ @@ -1152,8 +1148,11 @@ static void multifd_recv_terminate_threads(Error *err) MultiFDRecvParams *p = &multifd_recv_state->params[i]; qemu_mutex_lock(&p->mutex); - p->quit = true; - qemu_sem_post(&p->sem); + /* We could arrive here for two reasons: + - normal quit, i.e. everything went fine, just finished + - error quit: We close the channels so the channel threads + finish the qio_channel_read_all_eof() */ + qio_channel_shutdown(p->c, QIO_CHANNEL_SHUTDOWN_BOTH, NULL); qemu_mutex_unlock(&p->mutex); } } @@ -1176,7 +1175,6 @@ int multifd_load_cleanup(Error **errp) object_unref(OBJECT(p->c)); p->c = NULL; qemu_mutex_destroy(&p->mutex); - qemu_sem_destroy(&p->sem); qemu_sem_destroy(&p->sem_sync); g_free(p->name); p->name = NULL; @@ -1299,9 +1297,7 @@ int multifd_load_setup(void) MultiFDRecvParams *p = &multifd_recv_state->params[i]; qemu_mutex_init(&p->mutex); - qemu_sem_init(&p->sem, 0); qemu_sem_init(&p->sem_sync, 0); - p->quit = false; p->id = i; p->pages = multifd_pages_init(page_count); p->packet_len = sizeof(MultiFDPacket_t) -- 2.17.1