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[Qemu-devel] [PATCH] cpus: run work items for all vCPUs if single-thread
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH] cpus: run work items for all vCPUs if single-threaded |
Date: |
Wed, 14 Nov 2018 12:44:00 +0100 |
This avoids the following deadlock:
1) a thread calls run_on_cpu for CPU 2 from a timer, and 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 2 never runs the work item
4) run_on_cpu never completes
Signed-off-by: Paolo Bonzini <address@hidden>
---
cpus.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/cpus.c b/cpus.c
index a2b33ccb29..0ddeeefc14 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();
}
--
2.17.1
- [Qemu-devel] [PATCH] cpus: run work items for all vCPUs if single-threaded,
Paolo Bonzini <=