Re: [Qemu-devel] [RFC][PATCH] Register Linux dyntick timer as per-thread signal

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-06-16 17:24, Alexandre Raymond wrote:
> Hi Jan,
> 
> On Thu, Jun 16, 2011 at 5:31 AM, Jan Kiszka <jan.kiszka@siemens.com> wrote:
>> Ingo Molnar pointed out that sending the timer signal to the whole
>> process, just blocking it everywhere, is suboptimal with an increasing
>> number of threads. QEMU is using this pattern so far.
> 
> I am not familiar with this code, but don't you already need to block
> SIGALRM properly in all threads for OSes != Linux ? If so, isn't this
> patch redundant?

Yes, we still need to block for the sake of non-Linux UNIX or
pre-signalfd Linux. That blocking becomes in fact redundant in the
signalfd case, but that's both harmless and not worth optimizing. The
key is that per-thread signals do not care about other threads having
them blocked or not, they only deal with the target thread.

Jan

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