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srcu: Add SRCU_READ_FLAVOR_SLOWGP to flag need for synchronize_rcu()

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This commit switches from a direct test of SRCU_READ_FLAVOR_LITE to a new
SRCU_READ_FLAVOR_SLOWGP macro to check for substituting synchronize_rcu()
for smp_mb() in SRCU grace periods.  Right now, SRCU_READ_FLAVOR_SLOWGP
is exactly SRCU_READ_FLAVOR_LITE, but the addition of the _fast() flavor
of SRCU will change that.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: <bpf@vger.kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
This commit is contained in:
Paul E. McKenney 2025-01-08 06:48:15 -08:00 committed by Boqun Feng
parent 780818a681
commit 4d86b1e7e1
2 changed files with 6 additions and 3 deletions
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3
include/linux/srcu.h
View File

@ -49,6 +49,9 @@ int init_srcu_struct(struct srcu_struct *ssp);
#define SRCU_READ_FLAVOR_LITE 0x4 // srcu_read_lock_lite().
#define SRCU_READ_FLAVOR_ALL (SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_NMI | \
SRCU_READ_FLAVOR_LITE) // All of the above.
#define SRCU_READ_FLAVOR_SLOWGP SRCU_READ_FLAVOR_LITE
// Flavors requiring synchronize_rcu()
// instead of smp_mb().
#ifdef CONFIG_TINY_SRCU
#include <linux/srcutiny.h>

6
kernel/rcu/srcutree.c
View File

@ -449,7 +449,7 @@ static bool srcu_readers_lock_idx(struct srcu_struct *ssp, int idx, bool gp, uns
}
WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask - 1)),
"Mixed reader flavors for srcu_struct at %ps.\n", ssp);
if (mask & SRCU_READ_FLAVOR_LITE && !gp)
if (mask & SRCU_READ_FLAVOR_SLOWGP && !gp)
return false;
return sum == unlocks;
}
@ -487,7 +487,7 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *ssp, int idx)
unsigned long unlocks;
unlocks = srcu_readers_unlock_idx(ssp, idx, &rdm);
did_gp = !!(rdm & SRCU_READ_FLAVOR_LITE);
did_gp = !!(rdm & SRCU_READ_FLAVOR_SLOWGP);
/*
* Make sure that a lock is always counted if the corresponding
@ -1205,7 +1205,7 @@ static bool srcu_should_expedite(struct srcu_struct *ssp)
check_init_srcu_struct(ssp);
/* If _lite() readers, don't do unsolicited expediting. */
if (this_cpu_read(ssp->sda->srcu_reader_flavor) & SRCU_READ_FLAVOR_LITE)
if (this_cpu_read(ssp->sda->srcu_reader_flavor) & SRCU_READ_FLAVOR_SLOWGP)
return false;
/* If the local srcu_data structure has callbacks, not idle. */
sdp = raw_cpu_ptr(ssp->sda);