Re: [Qemu-devel] [PATCH v2 1/4] coroutine: introduce coroutines

[Stefan Hajnoczi]

On Thu, May 12, 2011 at 7:12 PM, Blue Swirl <address@hidden> wrote:
> On Thu, May 12, 2011 at 12:54 PM, Stefan Hajnoczi
> <address@hidden> wrote:
>> diff --git a/coroutine-ucontext.c b/coroutine-ucontext.c
>> new file mode 100644
>> index 0000000..3b14ebf
>> --- /dev/null
>> +++ b/coroutine-ucontext.c
>> @@ -0,0 +1,73 @@
>> +/*
>> + * ucontext coroutine initialization code
>> + *
>> + * Copyright (C) 2006  Anthony Liguori <address@hidden>
>> + * Copyright (C) 2011  Kevin Wolf <address@hidden>
>> + *
>> + * This library is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU Lesser General Public
>> + * License as published by the Free Software Foundation; either
>> + * version 2.0 of the License, or (at your option) any later version.
>> + *
>> + * This library is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * Lesser General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU Lesser General Public
>> + * License along with this library; if not, write to the Free Software
>> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  
>> 02110-1301 USA
>
> Please use the web link version.

Will update in v3.

>> + */
>> +
>> +/* XXX Is there a nicer way to disable glibc's stack check for longjmp? */
>
> What is the problem?

Kevin?

>> +static __thread Coroutine leader;
>
> $ cat thread.c
> static __thread int sigusr1_wfd;
> $ gcc thread.c -c -pthread
> thread.c:1: error: thread-local storage not supported for this target
> $ gcc -v
> Reading specs from
> /usr/bin/../lib/gcc-lib/sparc64-unknown-openbsd4.9/4.2.1/specs
> Target: sparc64-unknown-openbsd4.9
> Configured with: OpenBSD/sparc64 system compiler
> Thread model: posix
> gcc version 4.2.1 20070719

We had the thread-local variables in as part of the gtk-vnc history of
this code.  In QEMU we don't need it:

"Note that coroutines never execute concurrently and should only be used
from threads which hold the global mutex."

So I will remove the thread-local attribute.  Thank you for testing
that platform.

>> diff --git a/trace-events b/trace-events
>> index 4f965e2..2d4db05 100644
>> --- a/trace-events
>> +++ b/trace-events
>> @@ -361,3 +361,8 @@ disable milkymist_uart_pulse_irq_tx(void) "Pulse IRQ TX"
>>  # hw/milkymist-vgafb.c
>>  disable milkymist_vgafb_memory_read(uint32_t addr, uint32_t value) "addr 
>> %08x value %08x"
>>  disable milkymist_vgafb_memory_write(uint32_t addr, uint32_t value) "addr 
>> %08x value %08x"
>> +
>> +# qemu-coroutine.c
>> +qemu_coroutine_enter(void *from, void *to, void *opaque) "from %p to %p 
>> opaque %p"
>> +qemu_coroutine_yield(void *from, void *to) "from %p to %p"
>> +qemu_coroutine_terminate(void *co) "self %p"
>
> Not disabled?

Good catch.

Stefan