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[Qemu-devel] [PULL 22/37] cpus.c: Fix race condition in cpu_stop_current
From: |
Peter Maydell |
Subject: |
[Qemu-devel] [PULL 22/37] cpus.c: Fix race condition in cpu_stop_current() |
Date: |
Mon, 7 Jan 2019 16:31:02 +0000 |
We use cpu_stop_current() to ensure the current CPU has stopped
from places like qemu_system_reset_request(). Unfortunately its
current implementation has a race. It calls qemu_cpu_stop(),
which sets cpu->stopped to true even though the CPU hasn't
actually stopped yet. The main thread will look at the flags
set by qemu_system_reset_request() and call pause_all_vcpus().
pause_all_vcpus() waits for every cpu to have cpu->stopped true,
so it can continue (and we will start the system reset operation)
before the vcpu thread has got back to its top level loop.
Instead, just set cpu->stop and call cpu_exit(). This will
cause the vcpu to exit back to the top level loop, and there
(as part of the wait_io_event code) it will call qemu_cpu_stop().
This fixes bugs where the reset request appeared to be ignored
or the CPU misbehaved because the reset operation started
to change vcpu state while the vcpu thread was still using it.
Signed-off-by: Peter Maydell <address@hidden>
Reviewed-by: Emilio G. Cota <address@hidden>
Tested-by: Jaap Crezee <address@hidden>
Message-id: address@hidden
---
cpus.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/cpus.c b/cpus.c
index 0ddeeefc14f..b09b7027126 100644
--- a/cpus.c
+++ b/cpus.c
@@ -2100,7 +2100,8 @@ void qemu_init_vcpu(CPUState *cpu)
void cpu_stop_current(void)
{
if (current_cpu) {
- qemu_cpu_stop(current_cpu, true);
+ current_cpu->stop = true;
+ cpu_exit(current_cpu);
}
}
--
2.19.2
- Re: [Qemu-devel] [PULL 10/37] gdbstub: add multiprocess support to Xfer:features:read:, (continued)
- [Qemu-devel] [PULL 11/37] gdbstub: add multiprocess support to gdb_vm_state_change(), Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 14/37] gdbstub: add support for vAttach packets, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 17/37] gdbstub: add multiprocess extension support, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 15/37] gdbstub: processes initialization on new peer connection, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 19/37] Revert "armv7m: Guard against no -kernel argument", Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 12/37] gdbstub: add multiprocess support to 'D' packets, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 13/37] gdbstub: add support for extended mode packet, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 20/37] hw/arm: versal: Plug memory leaks, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 18/37] arm/xlnx-zynqmp: put APUs and RPUs in separate CPU clusters, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 22/37] cpus.c: Fix race condition in cpu_stop_current(),
Peter Maydell <=
- [Qemu-devel] [PULL 16/37] gdbstub: gdb_set_stop_cpu: ignore request when process is not attached, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 21/37] MAINTAINERS: Add ARM-related files for hw/[misc|input|timer]/, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 24/37] qtest: Add set_irq_in command to set IRQ/GPIO level, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 23/37] hw/arm/allwinner-a10: Add the 'A' SRAM and the SRAM controller, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 27/37] arm: Instantiate NRF51 random number generator, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 25/37] arm: Add header to host common definition for nRF51 SOC peripherals, Peter Maydell, 2019/01/07
- [Qemu-devel] [PULL 30/37] tests/microbit-test: Add Tests for nRF51 GPIO, Peter Maydell, 2019/01/07