Re: [PATCH v2 06/21] nptl: i386: Fix Race conditions in pthread cancellation (BZ#12683)

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

On 06/05/2018 23:49, Zack Weinberg wrote:
> On 26 Feb 2018, Adhemerval Zanella wrote:
>> This patch adds the i386 modifications required for the BZ#12683.
>> It basically provides the required ucontext_get_pc symbol, add the
>> cancelable syscall wrapper and fix a thread atomic update macro.
> 
> This also seems fine.
> 
>> On i386 an arch-specific cancellation implementation is required
>> because depending of the glibc configuration and underlying kernel
>> the syscall may be done using a vDSO symbol (__kernel_vsyscall).
> ...
>> Also, since glibc supports i486, the old 'int 0x80' should be used
>> in the syscall wrapper.  One option could make minimum default chip
>> to pentium II (which implements sysenter) or add a runtime check
>> on syscall_cancel.S to use 'int 0x80' or sysenter.
> 
> If I remember correctly, there can be only one 'sysenter' instruction
> in the entire user address space, due to awkward limitations of the
> interface it presents to the kernel.  That was why __kernel_vsyscall
> was added in the first place.
> 
> We can probably live with using int 0x80 for these syscalls that may
> well be blocking anyway.
> 
>> Similar to x86_64, it also remove bogus arch-specific
>> THREAD_ATOMIC_BIT_SET where it always reference to current thread
>> instead of the one referenced by input 'descr' argument.
> 
> Same comment as for x86_64 -- shouldn't we get rid of or repair _all_ of
> the THREAD_ATOMIC_ macros that don't honor their arguments?
> 
> zw
> 

Alright, I will remove then in an extra patch as well.