diff options
Diffstat (limited to 'src/backend/port/sysv_shmem.c')
| -rw-r--r-- | src/backend/port/sysv_shmem.c | 38 |
1 files changed, 21 insertions, 17 deletions
diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 968506dd516..dab2920ad61 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -390,11 +390,12 @@ PGSharedMemoryAttach(IpcMemoryId shmId, /* * Try to attach to the segment and see if it matches our data directory. - * This avoids key-conflict problems on machines that are running several - * postmasters under the same userid and port number. (That would not - * ordinarily happen in production, but it can happen during parallel - * testing. Since our test setups don't open any TCP ports on Unix, such - * cases don't conflict otherwise.) + * This avoids any risk of duplicate-shmem-key conflicts on machines that + * are running several postmasters under the same userid. + * + * (When we're called from PGSharedMemoryCreate, this stat call is + * duplicative; but since this isn't a high-traffic case it's not worth + * trying to optimize.) */ if (stat(DataDir, &statbuf) < 0) return SHMSTATE_ANALYSIS_FAILURE; /* can't stat; be conservative */ @@ -617,12 +618,9 @@ AnonymousShmemDetach(int status, Datum arg) * we do not fail upon collision with foreign shmem segments. The idea here * is to detect and re-use keys that may have been assigned by a crashed * postmaster or backend. - * - * The port number is passed for possible use as a key (for SysV, we use - * it to generate the starting shmem key). */ PGShmemHeader * -PGSharedMemoryCreate(Size size, int port, +PGSharedMemoryCreate(Size size, PGShmemHeader **shim) { IpcMemoryKey NextShmemSegID; @@ -631,6 +629,17 @@ PGSharedMemoryCreate(Size size, int port, struct stat statbuf; Size sysvsize; + /* + * We use the data directory's ID info (inode and device numbers) to + * positively identify shmem segments associated with this data dir, and + * also as seeds for searching for a free shmem key. + */ + if (stat(DataDir, &statbuf) < 0) + ereport(FATAL, + (errcode_for_file_access(), + errmsg("could not stat data directory \"%s\": %m", + DataDir))); + /* Complain if hugepages demanded but we can't possibly support them */ #if !defined(MAP_HUGETLB) if (huge_pages == HUGE_PAGES_ON) @@ -659,10 +668,10 @@ PGSharedMemoryCreate(Size size, int port, /* * Loop till we find a free IPC key. Trust CreateDataDirLockFile() to * ensure no more than one postmaster per data directory can enter this - * loop simultaneously. (CreateDataDirLockFile() does not ensure that, - * but prefer fixing it over coping here.) + * loop simultaneously. (CreateDataDirLockFile() does not entirely ensure + * that, but prefer fixing it over coping here.) */ - NextShmemSegID = 1 + port * 1000; + NextShmemSegID = statbuf.st_ino; for (;;) { @@ -748,11 +757,6 @@ PGSharedMemoryCreate(Size size, int port, hdr->dsm_control = 0; /* Fill in the data directory ID info, too */ - if (stat(DataDir, &statbuf) < 0) - ereport(FATAL, - (errcode_for_file_access(), - errmsg("could not stat data directory \"%s\": %m", - DataDir))); hdr->device = statbuf.st_dev; hdr->inode = statbuf.st_ino; |