[lttng-dev] [PATCH 2/2] urcu: add notice to URCU_TLS() for it is not async-signal-safe

[Lai Jiangshan]

On 08/10/2012 04:02 AM, Mathieu Desnoyers wrote:
> Looking at the result of a quick google search:
> 
> http://curl.haxx.se/mail/lib-2006-09/0224.html
> http://www.slamb.org/projects/sigsafe/api/patternref.html
> 
> "Additionally, it makes the same assumption as all other methods for
> handling thread-directed signals (with the exception of kevent(2)
> handling), that pthread_getspecific(2) is async signal-safe. This is not
> guaranteed by SUSv3."
> 
> and
> 
> https://groups.google.com/forum/?fromgroups#!topic/comp.os.linux.development/nZfmndKbzJw[1-25]
> 
> it looks like using pthread_getspecific from a signal handler is not
> always safe, mainly due to possible use of sigaltstack. So disabling
> signals works for the "pthread_key_create" part, but we still have an
> issue with pthread_getspecific.
> 
> Ideas are welcome on how to best deal with this issue.

What's the problem with disabling signals + pthread_getspecific()?
Waht's the problem with disabling signals + __tls_access_ ## name()?