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| author | Paul E. McKenney <paulmck@kernel.org> | 2024-10-15 09:11:01 -0700 |
|---|---|---|
| committer | Frederic Weisbecker <frederic@kernel.org> | 2024-11-12 15:42:20 +0100 |
| commit | c2f9467c77941cae5a41aa10c06ff0d5b00f69f9 (patch) | |
| tree | d102f0e4270a7a9ad4c63f356e33ebbd9309b1fc /kernel/rcu | |
| parent | 365f34483be33a9d0151c06ac39627d7927210d9 (diff) | |
| download | lwn-c2f9467c77941cae5a41aa10c06ff0d5b00f69f9.tar.gz lwn-c2f9467c77941cae5a41aa10c06ff0d5b00f69f9.zip | |
srcu: Bit manipulation changes for additional reader flavor
Currently, there are only two flavors of readers, normal and NMI-safe.
Very straightforward state updates suffice to check for erroneous
mixing of reader flavors on a given srcu_struct structure. This commit
upgrades the checking in preparation for the addition of light-weight
(as in memory-barrier-free) readers.
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>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/srcutree.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index f259dd834272..9774bc500de5 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -462,7 +462,7 @@ static unsigned long srcu_readers_unlock_idx(struct srcu_struct *ssp, int idx) if (IS_ENABLED(CONFIG_PROVE_RCU)) mask = mask | READ_ONCE(cpuc->srcu_reader_flavor); } - WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask >> 1)), + WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask - 1)), "Mixed NMI-safe readers for srcu_struct at %ps.\n", ssp); return sum; } @@ -712,8 +712,9 @@ void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) sdp = raw_cpu_ptr(ssp->sda); old_reader_flavor_mask = READ_ONCE(sdp->srcu_reader_flavor); if (!old_reader_flavor_mask) { - WRITE_ONCE(sdp->srcu_reader_flavor, reader_flavor_mask); - return; + old_reader_flavor_mask = cmpxchg(&sdp->srcu_reader_flavor, 0, reader_flavor_mask); + if (!old_reader_flavor_mask) + return; } WARN_ONCE(old_reader_flavor_mask != reader_flavor_mask, "CPU %d old state %d new state %d\n", sdp->cpu, old_reader_flavor_mask, reader_flavor_mask); } |