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ck_swlock: First round fixes for ck_swlock.

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- Add necessary memory barriers.
- Style conformance.
ck_pring
Samy Al Bahra 11 years ago
parent 9732e2bdb3
commit 82f33b3fe9
1 changed files with 28 additions and 30 deletions
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58
include/ck_swlock.h
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@ -1,5 +1,6 @@
/* /*
* Copyright 2011-2014 Samy Al Bahra. * Copyright 2014 Samy Al Bahra.
* Copyright 2014 Jaidev Sridhar.
* All rights reserved. * All rights reserved.
* *
* Redistribution and use in source and binary forms, with or without * Redistribution and use in source and binary forms, with or without
@ -28,6 +29,7 @@
#define _CK_SWLOCK_H #define _CK_SWLOCK_H
#include <ck_elide.h> #include <ck_elide.h>
#include <ck_limits.h>
#include <ck_pr.h> #include <ck_pr.h>
#include <stdbool.h> #include <stdbool.h>
#include <stddef.h> #include <stddef.h>
@ -39,7 +41,7 @@ struct ck_swlock {
typedef struct ck_swlock ck_swlock_t; typedef struct ck_swlock ck_swlock_t;
#define CK_SWLOCK_INITIALIZER {0, 0} #define CK_SWLOCK_INITIALIZER {0, 0}
#define CK_SWLOCK_LATCH_BIT (1 << 31) #define CK_SWLOCK_LATCH_BIT (1UL << 31)
#define CK_SWLOCK_READER_BITS (UINT32_MAX ^ CK_SWLOCK_LATCH_BIT) #define CK_SWLOCK_READER_BITS (UINT32_MAX ^ CK_SWLOCK_LATCH_BIT)
CK_CC_INLINE static void CK_CC_INLINE static void
@ -48,7 +50,6 @@ ck_swlock_init(struct ck_swlock *rw)
rw->writer = 0; rw->writer = 0;
rw->n_readers = 0; rw->n_readers = 0;
ck_pr_fence_store();
return; return;
} }
@ -56,6 +57,7 @@ CK_CC_INLINE static void
ck_swlock_write_unlock(ck_swlock_t *rw) ck_swlock_write_unlock(ck_swlock_t *rw)
{ {
ck_pr_fence_release();
ck_pr_store_32(&rw->writer, 0); ck_pr_store_32(&rw->writer, 0);
return; return;
} }
@ -64,6 +66,7 @@ CK_CC_INLINE static bool
ck_swlock_locked_writer(ck_swlock_t *rw) ck_swlock_locked_writer(ck_swlock_t *rw)
{ {
ck_pr_fence_load();
return ck_pr_load_32(&rw->writer); return ck_pr_load_32(&rw->writer);
} }
@ -79,11 +82,8 @@ ck_swlock_write_downgrade(ck_swlock_t *rw)
CK_CC_INLINE static bool CK_CC_INLINE static bool
ck_swlock_locked(ck_swlock_t *rw) ck_swlock_locked(ck_swlock_t *rw)
{ {
uint32_t r;
r = ck_pr_load_32(&rw->writer);
return ck_pr_load_32(&rw->n_readers) | r; return ck_pr_load_32(&rw->n_readers) | ck_pr_load_32(&rw->writer);
} }
CK_CC_INLINE static bool CK_CC_INLINE static bool
@ -127,10 +127,9 @@ ck_swlock_write_latch(ck_swlock_t *rw)
ck_pr_fence_atomic_load(); ck_pr_fence_atomic_load();
while (ck_pr_cas_32(&rw->n_readers, 0, CK_SWLOCK_LATCH_BIT) == false) { /* Stall until readers have seen the latch and cleared. */
/* Stall until readers have seen the latch and cleared */ while (ck_pr_cas_32(&rw->n_readers, 0, CK_SWLOCK_LATCH_BIT) == false)
ck_pr_stall(); ck_pr_stall();
}
return; return;
} }
@ -140,9 +139,7 @@ ck_swlock_write_unlatch(ck_swlock_t *rw)
{ {
ck_pr_store_32(&rw->n_readers, 0); ck_pr_store_32(&rw->n_readers, 0);
ck_swlock_write_unlock(rw); ck_swlock_write_unlock(rw);
return; return;
} }
@ -157,9 +154,10 @@ ck_swlock_read_trylock(ck_swlock_t *rw)
if (ck_pr_load_32(&rw->writer) != 0) if (ck_pr_load_32(&rw->writer) != 0)
return false; return false;
if (ck_pr_faa_32(&rw->n_readers, 1) & CK_SWLOCK_LATCH_BIT) { ck_pr_fence_load_atomic();
if (ck_pr_faa_32(&rw->n_readers, 1) & CK_SWLOCK_LATCH_BIT)
return false; return false;
}
/* /*
* Serialize with respect to concurrent write * Serialize with respect to concurrent write
@ -211,12 +209,15 @@ ck_swlock_read_latchlock(ck_swlock_t *rw)
{ {
for (;;) { for (;;) {
while (ck_pr_load_32(&rw->writer) != 0) while (ck_pr_load_32(&rw->writer) != 0)
ck_pr_stall(); ck_pr_stall();
/* Writer has latched, stall the reader */
if (ck_pr_faa_32(&rw->n_readers, 1) & CK_SWLOCK_LATCH_BIT) { if (ck_pr_faa_32(&rw->n_readers, 1) & CK_SWLOCK_LATCH_BIT) {
/* Writer has latched, stall the reader */ do {
ck_pr_stall();
} while (ck_pr_load_32(&rw->n_readers) & CK_SWLOCK_LATCH_BIT);
continue; continue;
} }
@ -243,14 +244,14 @@ ck_swlock_locked_reader(ck_swlock_t *rw)
{ {
ck_pr_fence_load(); ck_pr_fence_load();
return (ck_pr_load_32(&rw->n_readers) & CK_SWLOCK_READER_BITS); return ck_pr_load_32(&rw->n_readers) & CK_SWLOCK_READER_BITS;
} }
CK_CC_INLINE static void CK_CC_INLINE static void
ck_swlock_read_unlock(ck_swlock_t *rw) ck_swlock_read_unlock(ck_swlock_t *rw)
{ {
ck_pr_fence_load_atomic(); ck_pr_fence_release();
ck_pr_dec_32(&rw->n_readers); ck_pr_dec_32(&rw->n_readers);
return; return;
} }
@ -275,8 +276,7 @@ ck_swlock_recursive_write_lock(ck_swlock_recursive_t *rw)
{ {
ck_pr_store_32(&rw->rw.writer, 1); ck_pr_store_32(&rw->rw.writer, 1);
ck_pr_fence_store_load();
ck_pr_fence_atomic_load();
while (ck_pr_load_32(&rw->rw.n_readers) != 0) while (ck_pr_load_32(&rw->rw.n_readers) != 0)
ck_pr_stall(); ck_pr_stall();
@ -288,9 +288,9 @@ ck_swlock_recursive_write_lock(ck_swlock_recursive_t *rw)
CK_CC_INLINE static void CK_CC_INLINE static void
ck_swlock_recursive_write_latch(ck_swlock_recursive_t *rw) ck_swlock_recursive_write_latch(ck_swlock_recursive_t *rw)
{ {
ck_pr_store_32(&rw->rw.writer, 1);
ck_pr_fence_atomic_load(); ck_pr_store_32(&rw->rw.writer, 1);
ck_pr_fence_store_load();
while (ck_pr_cas_32(&rw->rw.n_readers, 0, CK_SWLOCK_LATCH_BIT) == false) while (ck_pr_cas_32(&rw->rw.n_readers, 0, CK_SWLOCK_LATCH_BIT) == false)
ck_pr_stall(); ck_pr_stall();
@ -304,8 +304,7 @@ ck_swlock_recursive_write_trylock(ck_swlock_recursive_t *rw)
{ {
ck_pr_store_32(&rw->rw.writer, 1); ck_pr_store_32(&rw->rw.writer, 1);
ck_pr_fence_store_load();
ck_pr_fence_atomic_load();
if (ck_pr_load_32(&rw->rw.n_readers) != 0) { if (ck_pr_load_32(&rw->rw.n_readers) != 0) {
ck_pr_store_32(&rw->rw.writer, 0); ck_pr_store_32(&rw->rw.writer, 0);
@ -320,21 +319,20 @@ CK_CC_INLINE static void
ck_swlock_recursive_write_unlock(ck_swlock_recursive_t *rw) ck_swlock_recursive_write_unlock(ck_swlock_recursive_t *rw)
{ {
if (--rw->wc == 0) { if (--rw->wc != 0)
ck_pr_fence_release(); return;
ck_pr_store_32(&rw->rw.writer, 0);
}
ck_pr_fence_release();
ck_pr_store_32(&rw->rw.writer, 0);
return; return;
} }
CK_CC_INLINE static void CK_CC_INLINE static void
ck_swlock_recursive_write_unlatch(ck_swlock_recursive_t *rw) ck_swlock_recursive_write_unlatch(ck_swlock_recursive_t *rw)
{ {
ck_pr_store_32(&rw->rw.n_readers, 0);
ck_pr_store_32(&rw->rw.n_readers, 0);
ck_swlock_recursive_write_unlock(rw); ck_swlock_recursive_write_unlock(rw);
return; return;
} }

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