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https://github.com/torvalds/linux
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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 */
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//
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// Code shared between 32 and 64 bit
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#include <asm/spec-ctrl.h>
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void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p);
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/*
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* This needs to be inline to optimize for the common case where no extra
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* work needs to be done.
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*/
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static inline void switch_to_extra(struct task_struct *prev,
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struct task_struct *next)
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{
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unsigned long next_tif = read_task_thread_flags(next);
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unsigned long prev_tif = read_task_thread_flags(prev);
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if (IS_ENABLED(CONFIG_SMP)) {
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/*
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* Avoid __switch_to_xtra() invocation when conditional
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* STIBP is disabled and the only different bit is
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* TIF_SPEC_IB. For CONFIG_SMP=n TIF_SPEC_IB is not
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* in the TIF_WORK_CTXSW masks.
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*/
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if (!static_branch_likely(&switch_to_cond_stibp)) {
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prev_tif &= ~_TIF_SPEC_IB;
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next_tif &= ~_TIF_SPEC_IB;
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}
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}
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/*
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* __switch_to_xtra() handles debug registers, i/o bitmaps,
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* speculation mitigations etc.
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*/
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if (unlikely(next_tif & _TIF_WORK_CTXSW_NEXT ||
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prev_tif & _TIF_WORK_CTXSW_PREV))
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__switch_to_xtra(prev, next);
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}
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