From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35127) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gReTn-0003iP-MK for qemu-devel@nongnu.org; Tue, 27 Nov 2018 09:36:48 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gReTm-0001EE-Kl for qemu-devel@nongnu.org; Tue, 27 Nov 2018 09:36:47 -0500 Received: from mail-wm1-x32a.google.com ([2a00:1450:4864:20::32a]:40531) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1gReTm-0001BX-EL for qemu-devel@nongnu.org; Tue, 27 Nov 2018 09:36:46 -0500 Received: by mail-wm1-x32a.google.com with SMTP id q26so22370363wmf.5 for ; Tue, 27 Nov 2018 06:36:46 -0800 (PST) Received: from 640k.localdomain ([93.56.166.5]) by smtp.gmail.com with ESMTPSA id n62sm2821869wmd.25.2018.11.27.06.36.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 27 Nov 2018 06:36:42 -0800 (PST) Sender: Paolo Bonzini From: Paolo Bonzini Date: Tue, 27 Nov 2018 15:36:24 +0100 Message-Id: <1543329397-48407-3-git-send-email-pbonzini@redhat.com> In-Reply-To: <1543329397-48407-1-git-send-email-pbonzini@redhat.com> References: <1543329397-48407-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PULL 02/15] cpus: run work items for all vCPUs if single-threaded List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org This avoids the following I/O thread deadlock: 1) the I/O thread calls run_on_cpu for CPU 3 from a timer. single_tcg_halt_cond is signaled 2) CPU 1 is running and exits. It finds no work item and enters CPU 2 3) because the I/O thread is stuck in run_on_cpu, the round-robin kick timer never triggers, and CPU 3 never runs the work item 4) run_on_cpu never completes Reviewed-by: Emilio G. Cota Signed-off-by: Paolo Bonzini --- cpus.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/cpus.c b/cpus.c index a2b33cc..0ddeeef 100644 --- a/cpus.c +++ b/cpus.c @@ -1220,16 +1220,20 @@ static void qemu_wait_io_event_common(CPUState *cpu) process_queued_cpu_work(cpu); } -static void qemu_tcg_rr_wait_io_event(CPUState *cpu) +static void qemu_tcg_rr_wait_io_event(void) { + CPUState *cpu; + while (all_cpu_threads_idle()) { stop_tcg_kick_timer(); - qemu_cond_wait(cpu->halt_cond, &qemu_global_mutex); + qemu_cond_wait(first_cpu->halt_cond, &qemu_global_mutex); } start_tcg_kick_timer(); - qemu_wait_io_event_common(cpu); + CPU_FOREACH(cpu) { + qemu_wait_io_event_common(cpu); + } } static void qemu_wait_io_event(CPUState *cpu) @@ -1562,7 +1566,7 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg) qemu_notify_event(); } - qemu_tcg_rr_wait_io_event(cpu ? cpu : first_cpu); + qemu_tcg_rr_wait_io_event(); deal_with_unplugged_cpus(); } -- 1.8.3.1