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srcu: Make Tiny SRCU explicitly disable preemption

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Because Tiny SRCU is used only in kernels built with either
CONFIG_PREEMPT_NONE=y or CONFIG_PREEMPT_VOLUNTARY=y, there has not
been any need for TINY SRCU to explicitly disable preemption.  However,
the prospect of lazy preemption changes that, and the lazy-preemption
patches do result in rcutorture runs finding both too-short grace periods
and grace-period hangs for Tiny SRCU.

This commit therefore adds the needed preempt_disable() and
preempt_enable() calls to Tiny SRCU.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Ankur Arora <ankur.a.arora@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
This commit is contained in:
Paul E. McKenney
2024-02-15 09:04:30 -08:00
committed by Uladzislau Rezki (Sony)
parent c1ec7c1580
commit 65b4a59557
2 changed files with 28 additions and 5 deletions
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2
include/linux/srcutiny.h
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@@ -64,8 +64,10 @@ static inline int __srcu_read_lock(struct srcu_struct *ssp)
{
int idx;
preempt_disable(); // Needed for PREEMPT_AUTO
idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1;
WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1);
preempt_enable();
return idx;
}