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Date: Mon, 21 May 2018 17:49:31 +0200
From: Michael Walle <michael@walle.cc>
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Subject: Re: [Qemu-devel] [PATCH v2 2/2] target/lm32: hold BQL in gdbstub
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>, Paolo Bonzini <pbonzini@redhat.com>, =?UTF-8?Q?Alex_Benn=C3=A9e?= <alex.bennee@linaro.org>, qemu-stable <qemu-stable@nongnu.org>

Am 2018-05-21 14:25, schrieb Peter Maydell:
> On 21 May 2018 at 13:21, Michael Walle <michael@walle.cc> wrote:
>> Changing the IP/IM registers may cause interrupts, so hold the BQL.
>> 
>> Cc: qemu-stable@nongnu.org
>> Signed-off-by: Michael Walle <michael@walle.cc>
>> ---
>>  target/lm32/gdbstub.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>> 
>> diff --git a/target/lm32/gdbstub.c b/target/lm32/gdbstub.c
>> index cf929dd392..dac9418a2b 100644
>> --- a/target/lm32/gdbstub.c
>> +++ b/target/lm32/gdbstub.c
>> @@ -18,6 +18,7 @@
>>   * License along with this library; if not, see 
>> <http://www.gnu.org/licenses/>.
>>   */
>>  #include "qemu/osdep.h"
>> +#include "qemu/main-loop.h"
>>  #include "qemu-common.h"
>>  #include "cpu.h"
>>  #include "exec/gdbstub.h"
>> @@ -82,10 +83,14 @@ int lm32_cpu_gdb_write_register(CPUState *cs, 
>> uint8_t *mem_buf, int n)
>>              env->ie = tmp;
>>              break;
>>          case 37:
>> +            qemu_mutex_lock_iothread();
>>              lm32_pic_set_im(env->pic_state, tmp);
>> +            qemu_mutex_unlock_iothread();
>>              break;
>>          case 38:
>> +            qemu_mutex_lock_iothread();
>>              lm32_pic_set_ip(env->pic_state, tmp);
>> +            qemu_mutex_unlock_iothread();
>>              break;
>>          }
>>      }
> 
> Are you sure this is necessary? I would have expected the gdbstub to
> be operating under the qemu lock anyway.


You're right. The gdbstub is already holding the lock. So i'll drop this 
and send the pull request right now.

-michael