Commit 4d86b1e7 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Boqun Feng
Browse files

srcu: Add SRCU_READ_FLAVOR_SLOWGP to flag need for synchronize_rcu() 



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: default avatarPaul 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: default avatarBoqun Feng <boqun.feng@gmail.com>
parent 780818a6

include/linux/srcu.h

+3 −0
Original line number Diff line number Diff line
@@ -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>

kernel/rcu/srcutree.c

+3 −3
Original line number Diff line number Diff line
@@ -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);