On 26/10/2021 19.10, Richard Henderson wrote:
On 10/26/21 9:34 AM, Stefan Hajnoczi wrote:
On Tue, Oct 26, 2021 at 08:10:16AM -0700, Richard Henderson wrote:
On 10/26/21 6:22 AM, Stefan Hajnoczi wrote:
If "safe" TLS variables are opt-in then we'll likely have obscure bugs
when code changes to access a TLS variable that was previously never
accessed from a coroutine. There is no compiler error and no way to
detect this. When it happens debugging it is painful.
Co-routines are never used in user-only builds.
If developers have the choice of using __thread then bugs can slip
through.
Huh? How. No, really.
Are you concerned about performance, the awkwardness of calling
getters/setters, or something else for qemu-user?
Awkwardness first, performance second.
I'll also note that coroutines never run on vcpu threads, only io threads.
So I'll resist any use of these interfaces in TCG as well.
Would it maybe make sense to tweak check_patch.pl to forbid __thread in
certain folders only, e.g. block/ and util/ (i.e. where we know that there
might be code that the iothreads are using)?
Thomas
