Re: [PATCH] linux-user: Don't assume 0 is not a valid host timer_t value

[Laurent Vivier <laurent@vivier.eu>]

Le 09/08/2022 à 11:51, Peter Maydell a écrit :
> Laurent, ping ?

Sorry, I didn't see your message. I'm going to apply it if it's ok to go into rc3?

Thanks,
Laurent

> 
> thanks
> -- PMM
> 
> On Mon, 1 Aug 2022 at 12:43, Peter Maydell <peter.maydell@linaro.org> wrote:
>>
>> On Mon, 25 Jul 2022 at 12:13, Daniel P. Berrangé <berrange@redhat.com> wrote:
>>>
>>> On Mon, Jul 25, 2022 at 12:00:35PM +0100, Peter Maydell wrote:
>>>> For handling guest POSIX timers, we currently use an array
>>>> g_posix_timers[], whose entries are a host timer_t value, or 0 for
>>>> "this slot is unused".  When the guest calls the timer_create syscall
>>>> we look through the array for a slot containing 0, and use that for
>>>> the new timer.
>>>>
>>>> This scheme assumes that host timer_t values can never be zero.  This
>>>> is unfortunately not a valid assumption -- for some host libc
>>>> versions, timer_t values are simply indexes starting at 0.  When
>>>> using this kind of host libc, the effect is that the first and second
>>>> timers end up sharing a slot, and so when the guest tries to operate
>>>> on the first timer it changes the second timer instead.
>>>
>>> For sake of historical record, could you mention here which specific
>>> libc impl / version highlights the problem.
>>
>> How about:
>>
>> "This can happen if you are using glibc's backwards-compatible
>> 'timer_t is an integer' compat code for some reason. This happens
>> when a glibc newer than 2.3.3 is used for a program that was
>> linked to work with glibc 2.2 to 2.3.3."
>>
>> Laurent, I'm going to assume you don't need a v2 sending just
>> for a commit message tweak, unless you'd like me to do that.
>>
>> thanks
>> -- PMM
>