diff options
Diffstat (limited to 'src/backend/storage/ipc/shm_toc.c')
| -rw-r--r-- | src/backend/storage/ipc/shm_toc.c | 40 |
1 files changed, 22 insertions, 18 deletions
diff --git a/src/backend/storage/ipc/shm_toc.c b/src/backend/storage/ipc/shm_toc.c index 5e290df3366..50334cd7978 100644 --- a/src/backend/storage/ipc/shm_toc.c +++ b/src/backend/storage/ipc/shm_toc.c @@ -6,7 +6,7 @@ * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * src/include/storage/shm_toc.c + * src/backend/storage/ipc/shm_toc.c * *------------------------------------------------------------------------- */ @@ -20,16 +20,16 @@ typedef struct shm_toc_entry { uint64 key; /* Arbitrary identifier */ - uint64 offset; /* Bytes offset */ + Size offset; /* Offset, in bytes, from TOC start */ } shm_toc_entry; struct shm_toc { - uint64 toc_magic; /* Magic number for this TOC */ + uint64 toc_magic; /* Magic number identifying this TOC */ slock_t toc_mutex; /* Spinlock for mutual exclusion */ Size toc_total_bytes; /* Bytes managed by this TOC */ Size toc_allocated_bytes; /* Bytes allocated of those managed */ - Size toc_nentry; /* Number of entries in TOC */ + uint32 toc_nentry; /* Number of entries in TOC */ shm_toc_entry toc_entry[FLEXIBLE_ARRAY_MEMBER]; }; @@ -53,7 +53,7 @@ shm_toc_create(uint64 magic, void *address, Size nbytes) /* * Attach to an existing table of contents. If the magic number found at - * the target address doesn't match our expectations, returns NULL. + * the target address doesn't match our expectations, return NULL. */ extern shm_toc * shm_toc_attach(uint64 magic, void *address) @@ -64,7 +64,7 @@ shm_toc_attach(uint64 magic, void *address) return NULL; Assert(toc->toc_total_bytes >= toc->toc_allocated_bytes); - Assert(toc->toc_total_bytes >= offsetof(shm_toc, toc_entry)); + Assert(toc->toc_total_bytes > offsetof(shm_toc, toc_entry)); return toc; } @@ -76,7 +76,7 @@ shm_toc_attach(uint64 magic, void *address) * just a way of dividing a single physical shared memory segment into logical * chunks that may be used for different purposes. * - * We allocated backwards from the end of the segment, so that the TOC entries + * We allocate backwards from the end of the segment, so that the TOC entries * can grow forward from the start of the segment. */ extern void * @@ -140,7 +140,7 @@ shm_toc_freespace(shm_toc *toc) /* * Insert a TOC entry. * - * The idea here is that process setting up the shared memory segment will + * The idea here is that the process setting up the shared memory segment will * register the addresses of data structures within the segment using this * function. Each data structure will be identified using a 64-bit key, which * is assumed to be a well-known or discoverable integer. Other processes @@ -155,17 +155,17 @@ shm_toc_freespace(shm_toc *toc) * data structure here. But the real idea here is just to give someone mapping * a dynamic shared memory the ability to find the bare minimum number of * pointers that they need to bootstrap. If you're storing a lot of stuff in - * here, you're doing it wrong. + * the TOC, you're doing it wrong. */ void shm_toc_insert(shm_toc *toc, uint64 key, void *address) { volatile shm_toc *vtoc = toc; - uint64 total_bytes; - uint64 allocated_bytes; - uint64 nentry; - uint64 toc_bytes; - uint64 offset; + Size total_bytes; + Size allocated_bytes; + Size nentry; + Size toc_bytes; + Size offset; /* Relativize pointer. */ Assert(address > (void *) toc); @@ -181,7 +181,8 @@ shm_toc_insert(shm_toc *toc, uint64 key, void *address) /* Check for memory exhaustion and overflow. */ if (toc_bytes + sizeof(shm_toc_entry) > total_bytes || - toc_bytes + sizeof(shm_toc_entry) < toc_bytes) + toc_bytes + sizeof(shm_toc_entry) < toc_bytes || + nentry >= PG_UINT32_MAX) { SpinLockRelease(&toc->toc_mutex); ereport(ERROR, @@ -220,10 +221,13 @@ shm_toc_insert(shm_toc *toc, uint64 key, void *address) void * shm_toc_lookup(shm_toc *toc, uint64 key, bool noError) { - uint64 nentry; - uint64 i; + uint32 nentry; + uint32 i; - /* Read the number of entries before we examine any entry. */ + /* + * Read the number of entries before we examine any entry. We assume that + * reading a uint32 is atomic. + */ nentry = toc->toc_nentry; pg_read_barrier(); |