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Re: [Qemu-devel] [PATCH] main-loop: Don't lock starve io-threads when ma
From: |
Alex Bligh |
Subject: |
Re: [Qemu-devel] [PATCH] main-loop: Don't lock starve io-threads when main_loop_tlg has pending events |
Date: |
Tue, 8 Oct 2013 20:48:26 +0100 |
On 8 Oct 2013, at 20:10, Hans de Goede wrote:
> I noticed today that current qemu master would hang as soon as Xorg starts in
> the guest when using qxl + a Linux guest. This message would be printed:
> main-loop: WARNING: I/O thread spun for 1000 iterations
>
> And from then on the guest hangs and qemu consumes 100% cpu, bisecting pointed
> out commit 7b595f35d89d73bc69c35bf3980a89c420e8a44b:
> "aio / timers: Convert mainloop to use timeout"
>
> After looking at that commit I had a hunch the problem might be blocking
> main_loop_wait calls being turned into non-blocking ones (and thus never
> releasing the io-lock), a debug printf confirmed this was happening at
> the moment of the hang, so I wrote this patch which fixes the hang for me
> and seems like a good idea in general.
>
> Signed-off-by: Hans de Goede <address@hidden>
> ---
> main-loop.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/main-loop.c b/main-loop.c
> index c3c9c28..921c939 100644
> --- a/main-loop.c
> +++ b/main-loop.c
> @@ -480,6 +480,11 @@ int main_loop_wait(int nonblocking)
> timerlistgroup_deadline_ns(
> &main_loop_tlg));
>
> + /* When not non-blocking always allow io-threads to acquire the lock */
> + if (timeout != 0 && timeout_ns == 0) {
> + timeout_ns = 1;
> + }
> +
> ret = os_host_main_loop_wait(timeout_ns);
> qemu_iohandler_poll(gpollfds, ret);
> #ifdef CONFIG_SLIRP
I /think/ you might mean "if (!blocking && timeout_ns == 0)"
as timeout can be zero on a blocking call at this stage (i.e.
when there is a timer which has already expired.
I'm not entirely sure I understand the problem from your
description - I'll answer this in your subseqent message.
--
Alex Bligh
- Re: [Qemu-devel] [PATCH] main-loop: Don't lock starve io-threads when main_loop_tlg has pending events, (continued)
- Re: [Qemu-devel] [PATCH] main-loop: Don't lock starve io-threads when main_loop_tlg has pending events, Paolo Bonzini, 2013/10/09
- Re: [Qemu-devel] [PATCH] main-loop: Don't lock starve io-threads when main_loop_tlg has pending events, Alex Bligh, 2013/10/09
- Re: [Qemu-devel] [PATCH] main-loop: Don't lock starve io-threads when main_loop_tlg has pending events, Paolo Bonzini, 2013/10/09
- Re: [Qemu-devel] [PATCH] main-loop: Don't lock starve io-threads when main_loop_tlg has pending events, Alex Bligh, 2013/10/09
- Re: [Qemu-devel] [PATCH] main-loop: Don't lock starve io-threads when main_loop_tlg has pending events, Hans de Goede, 2013/10/09
- Re: [Qemu-devel] [PATCH] main-loop: Don't lock starve io-threads when main_loop_tlg has pending events, Hans de Goede, 2013/10/09
Re: [Qemu-devel] [PATCH] main-loop: Don't lock starve io-threads when main_loop_tlg has pending events,
Alex Bligh <=