mirror of
https://github.com/torvalds/linux.git
synced 2024-11-25 13:41:51 +00:00
dca99fb643
Some thread flags can be set remotely, and so even when IRQs are disabled, the flags can change under our feet. Generally this is unlikely to cause a problem in practice, but it is somewhat unsound, and KCSAN will legitimately warn that there is a data race. To avoid such issues, a snapshot of the flags has to be taken prior to using them. Some places already use READ_ONCE() for that, others do not. Convert them all to the new flag accessor helpers. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Paul E. McKenney <paulmck@kernel.org> Link: https://lore.kernel.org/r/20211129130653.2037928-12-mark.rutland@arm.com
40 lines
1.1 KiB
C
40 lines
1.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
//
|
|
// Code shared between 32 and 64 bit
|
|
|
|
#include <asm/spec-ctrl.h>
|
|
|
|
void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p);
|
|
|
|
/*
|
|
* This needs to be inline to optimize for the common case where no extra
|
|
* work needs to be done.
|
|
*/
|
|
static inline void switch_to_extra(struct task_struct *prev,
|
|
struct task_struct *next)
|
|
{
|
|
unsigned long next_tif = read_task_thread_flags(next);
|
|
unsigned long prev_tif = read_task_thread_flags(prev);
|
|
|
|
if (IS_ENABLED(CONFIG_SMP)) {
|
|
/*
|
|
* Avoid __switch_to_xtra() invocation when conditional
|
|
* STIBP is disabled and the only different bit is
|
|
* TIF_SPEC_IB. For CONFIG_SMP=n TIF_SPEC_IB is not
|
|
* in the TIF_WORK_CTXSW masks.
|
|
*/
|
|
if (!static_branch_likely(&switch_to_cond_stibp)) {
|
|
prev_tif &= ~_TIF_SPEC_IB;
|
|
next_tif &= ~_TIF_SPEC_IB;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* __switch_to_xtra() handles debug registers, i/o bitmaps,
|
|
* speculation mitigations etc.
|
|
*/
|
|
if (unlikely(next_tif & _TIF_WORK_CTXSW_NEXT ||
|
|
prev_tif & _TIF_WORK_CTXSW_PREV))
|
|
__switch_to_xtra(prev, next);
|
|
}
|