linux.git/include/linux/futex_types.h, branch master Linux kernel source tree futex: Add robust futex unlock IP range 2026-06-03T09:38:51+00:00 Thomas Gleixner tglx@kernel.org 2026-06-02T09:09:59+00:00 042df0c1d48609a85580dcbaff498c95ced20a5f There will be a VDSO function to unlock robust futexes in user space. The unlock sequence is racy vs. clearing the list_pending_op pointer in the tasks robust list head. To plug this race the kernel needs to know the instruction window. As the VDSO is per MM the addresses are stored in mm_struct::futex. Architectures which implement support for this have to update these addresses when the VDSO is (re)mapped and indicate the pending op pointer size which is matching the IP. Arguably this could be resolved by chasing mm->context->vdso->image, but that's architecture specific and requires to touch quite some cache lines. Having it in mm::futex reduces the cache line impact and avoids having yet another set of architecture specific functionality. To support multi size robust list applications (gaming) this provides two ranges when COMPAT is enabled. Signed-off-by: Thomas Gleixner <tglx@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: André Almeida <andrealmeid@igalia.com> Link: https://patch.msgid.link/20260602090535.718926819@kernel.org 
There will be a VDSO function to unlock robust futexes in user space. The
unlock sequence is racy vs. clearing the list_pending_op pointer in the
tasks robust list head. To plug this race the kernel needs to know the
instruction window. As the VDSO is per MM the addresses are stored in
mm_struct::futex.

Architectures which implement support for this have to update these
addresses when the VDSO is (re)mapped and indicate the pending op pointer
size which is matching the IP.

Arguably this could be resolved by chasing mm->context->vdso->image, but
that's architecture specific and requires to touch quite some cache
lines. Having it in mm::futex reduces the cache line impact and avoids
having yet another set of architecture specific functionality.

To support multi size robust list applications (gaming) this provides two
ranges when COMPAT is enabled.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: André Almeida <andrealmeid@igalia.com>
Link: https://patch.msgid.link/20260602090535.718926819@kernel.org
futex: Move futex related mm_struct data into a struct 2026-06-03T09:38:49+00:00 Thomas Gleixner tglx@kernel.org 2026-06-02T09:09:34+00:00 1f7f4816b9b05e5110bc1c8a05c3c478e2dae11b Having all these members in mm_struct along with the required #ifdeffery is annoying, does not allow efficient initializing of the data with memset() and makes extending it tedious. Move it into a data structure and fix up all usage sites. The extra struct for the private hash is intentional to make integration of other conditional mechanisms easier in terms of initialization and separation. Signed-off-by: Thomas Gleixner <tglx@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://patch.msgid.link/20260602090535.407756793@kernel.org 
Having all these members in mm_struct along with the required #ifdeffery is
annoying, does not allow efficient initializing of the data with
memset() and makes extending it tedious.

Move it into a data structure and fix up all usage sites.

The extra struct for the private hash is intentional to make integration of
other conditional mechanisms easier in terms of initialization and separation.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260602090535.407756793@kernel.org
futex: Move futex task related data into a struct 2026-06-03T09:38:49+00:00 Thomas Gleixner tglx@kernel.org 2026-06-02T09:09:25+00:00 c1ffc9c6e4f8a13dd68e97920c9a24d095c6e41a Having all these members in task_struct along with the required #ifdeffery is annoying, does not allow efficient initializing of the data with memset() and makes extending it tedious. Move it into a data structure and fix up all usage sites. Signed-off-by: Thomas Gleixner <tglx@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Reviewed-by: André Almeida <andrealmeid@igalia.com> Link: https://patch.msgid.link/20260602090535.308220888@kernel.org 
Having all these members in task_struct along with the required #ifdeffery
is annoying, does not allow efficient initializing of the data with
memset() and makes extending it tedious.

Move it into a data structure and fix up all usage sites.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: André Almeida <andrealmeid@igalia.com>
Link: https://patch.msgid.link/20260602090535.308220888@kernel.org