Date: Thu, 20 Jul 2023 17:22:07 +0300 From: Alexey Izbyshev <izbyshev@...ras.ru> To: musl@...ts.openwall.com Subject: Re: [PATCH] set tid address in fork On 2023-07-20 16:53, changdiankang wrote: > In pthrad_exit the exiting thread will hold the thread list lock, > and will unlock it in kernel by clear the tid address > &__thread_list_lock. > > A thread created by pthrad_create is created with clone syscall with > CLONE_CHILD_CLEARTID flag and &__thread_list_lock as child_tid > parameter. When the thread exits, the thread list lock can be woke up > (see man clone CLONE_CHILD_CLEARTID). > > But in fork, the main thread is created with fork syscall or with > clone syscall without CLONE_CHILD_CLEARTID flag. The > &__thread_list_lock > is not be set to tid address. So when the main thread exits, the thread > list lock can't be woke up by kernel. This may lead some problems when > other child threads try to hold this lock. For example, a child thread > blocks at waiting thread list lock when joining the main thread. > > To fix this issue, we should set &__thread_list_lock to the main thread > tid > address in fork. This bug has already been discovered, see https://www.openwall.com/lists/musl/2023/06/01/9. Alexey
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