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arch: arm: update thread options flag and CONTROL atomically

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Under FP shared registers mode (CONFIG_FP_SHARING=y),
a thread's user_options flag is checked during swap and
during stack fail check. Therefore, in k_float_disable()
we want to ensure that a thread won't be swapped-out with
K_FP_REGS flag cleared but still FP-active (CONTROL.FPCA
being not zero). To ensure that we temporarily disable
interrupts.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
This commit is contained in:
Ioannis Glaropoulos 2019-06-18 17:33:48 +02:00 committed by Andrew Boie
parent f70093afb8
commit 171272cf31
1 changed files with 14 additions and 0 deletions
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14
arch/arm/core/thread.c
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@ -351,9 +351,23 @@ int z_arch_float_disable(struct k_thread *thread)
/* Disable all floating point capabilities for the thread */
/* K_FP_REG flag is used in SWAP and stack check fail. Locking
* interrupts here prevents a possible context-switch or MPU
* fault to take an outdated thread user_options flag into
* account.
*/
int key = z_arch_irq_lock();
thread->base.user_options &= ~K_FP_REGS;
__set_CONTROL(__get_CONTROL() & (~CONTROL_FPCA_Msk));
/* No need to add an ISB barrier after setting the CONTROL
* register; z_arch_irq_unlock() already adds one.
*/
z_arch_irq_unlock(key);
return 0;
}
#endif /* CONFIG_FLOAT && CONFIG_FP_SHARING */