Re: enter/leave_critical_section() calls in the user space library

[Gregory Nutt]

One way to make this work correctly would be to remove the logmask as 
a global variable and, instead, put the logic mask in the group 
structure or in the TCB structure.  That would make logmask thread 
safe (in the second case).  This would be the preferred solution. This 
solution would work.  The other suggestions will not work and just 
implement more complex version of the broken code.
Actually, putting the logmask in TLS (with the errno) would be better 
solution.  In some configurations, at least, that would avoid a system call.