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authorPeter Zijlstra <peterz@infradead.org>2019-10-30 20:30:41 +0100
committerIngo Molnar <mingo@kernel.org>2020-02-11 13:10:56 +0100
commit7f26482a872c36b2ee87ea95b9dcd96e3d5805df (patch)
tree0a0e843a50333cc34780860e3378ecae2c5a52bf /include/linux/wait.h
parent75ff64572e497578e238fefbdff221c96f29067a (diff)
locking/percpu-rwsem: Remove the embedded rwsem
The filesystem freezer uses percpu-rwsem in a way that is effectively write_non_owner() and achieves this with a few horrible hacks that rely on the rwsem (!percpu) implementation. When PREEMPT_RT replaces the rwsem implementation with a PI aware variant this comes apart. Remove the embedded rwsem and implement it using a waitqueue and an atomic_t. - make readers_block an atomic, and use it, with the waitqueue for a blocking test-and-set write-side. - have the read-side wait for the 'lock' state to clear. Have the waiters use FIFO queueing and mark them (reader/writer) with a new WQ_FLAG. Use a custom wake_function to wake either a single writer or all readers until a writer. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Davidlohr Bueso <dbueso@suse.de> Acked-by: Will Deacon <will@kernel.org> Acked-by: Waiman Long <longman@redhat.com> Tested-by: Juri Lelli <juri.lelli@redhat.com> Link: https://lkml.kernel.org/r/20200204092403.GB14879@hirez.programming.kicks-ass.net
Diffstat (limited to 'include/linux/wait.h')
-rw-r--r--include/linux/wait.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/wait.h b/include/linux/wait.h
index 3283c8d02137..feeb6be5cad6 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -20,6 +20,7 @@ int default_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, int
#define WQ_FLAG_EXCLUSIVE 0x01
#define WQ_FLAG_WOKEN 0x02
#define WQ_FLAG_BOOKMARK 0x04
+#define WQ_FLAG_CUSTOM 0x08
/*
* A single wait-queue entry structure: