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Date: Wed, 11 Jun 2014 10:16:29 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 4/6] qemu-char: make writes thread-safe
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To: Fam Zheng <famz@redhat.com>
Cc: kwolf@redhat.com, kraxel@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com, lcapitulino@redhat.com

Il 11/06/2014 08:59, Fam Zheng ha scritto:
> On Tue, 06/03 18:39, Paolo Bonzini wrote:
>> diff --git a/qemu-char.c b/qemu-char.c
>> index b478a3d..dcd0765 100644
>> --- a/qemu-char.c
>> +++ b/qemu-char.c
>> @@ -121,7 +121,12 @@ void qemu_chr_be_generic_open(CharDriverState *s)
>>
>>  int qemu_chr_fe_write(CharDriverState *s, const uint8_t *buf, int len)
>>  {
>> -    return s->chr_write(s, buf, len);
>> +    int ret;
>> +
>> +    qemu_mutex_lock(&s->chr_write_lock);
>> +    ret = s->chr_write(s, buf, len);
>> +    qemu_mutex_unlock(&s->chr_write_lock);
>> +    return ret;
>>  }
>>
>>  int qemu_chr_fe_write_all(CharDriverState *s, const uint8_t *buf, int len)
>> @@ -129,6 +134,7 @@ int qemu_chr_fe_write_all(CharDriverState *s, const uint8_t *buf, int len)
>>      int offset = 0;
>>      int res;
>>
>> +    qemu_mutex_lock(&s->chr_write_lock);
>>      while (offset < len) {
>>          do {
>>              res = s->chr_write(s, buf + offset, len - offset);
>> @@ -147,6 +153,7 @@ int qemu_chr_fe_write_all(CharDriverState *s, const uint8_t *buf, int len)
>
> More context in the loop:
>
>               if (res == -1 && errno == EAGAIN) {
>                   g_usleep(100);
>               }
>           } while (res == -1 && errno == EAGAIN);
>
>           if (res == 0) {
>               break;
>           }
>
>           if (res < 0) {
> (*)           return res;
>           }
>
> Doesn't (*) need an unlock?

Indeed, thanks.

Paolo