On 03/06/2020 16:46, Vineet Gupta wrote: > On 5/29/20 9:49 AM, Adhemerval Zanella via Libc-alpha wrote: >>> + ; ----- child starts here --------- >>> + >>> + ; Setup TP register (only recent kernels v4.19+ do that) >>> + and.f 0, r12, CLONE_SETTLS >>> + mov.nz r25, r9 >> Do you still need to set it since the minimum supported kernel >> for ARC is 5.1 ? > > Right. > >> It should be safe for internal glibc usage, since for both pthread >> and posix_spawn it blocks all signals including SIGCANCEL and SIGXID. >> However this is still small race window if this is called directly >> with pthread cancellation or g*uid in multithread. > > I'm not sure what you mean above. Do you mean not doing this in glibc and even if > kernel support didn't exist should be safe internally ? At least for internal clone usage with CLONE_VM within glibc we explicit disable all signals (posix_spawn and pthread_create). > > fwiw as mentioned above kernel sets up TP for clone (SETTLS). I detested doing > that for a long time, give ABI implications but ended up doing it anyways due to > an actual race hit when running uClibc tst-kill6 [1] We explicit disable all signals during the create_thread call in pthread_create (b3cae39dcbfa2432b3f3aa28854d8ac57f0de1b8), so it should not happen on glibc anymore. However it is still an issue if application calls clone itself. > > [1] http://lists.infradead.org/pipermail/linux-snps-arc/2018-October/004480.html > _______________________________________________ linux-snps-arc mailing list linux-snps-arc@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/linux-snps-arc
