diff options
| -rw-r--r-- | src/backend/port/sysv_shmem.c | 30 | ||||
| -rw-r--r-- | src/include/port/linux.h | 13 |
2 files changed, 37 insertions, 6 deletions
diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 94e285ff2b1..8834c08bbec 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -10,7 +10,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/port/sysv_shmem.c,v 1.4.2.1 2003/11/30 21:56:36 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/port/sysv_shmem.c,v 1.4.2.2 2007/07/02 20:12:26 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -219,10 +219,6 @@ PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2) /* * We detect whether a shared memory segment is in use by seeing * whether it (a) exists and (b) has any processes are attached to it. - * - * If we are unable to perform the stat operation for a reason other than - * nonexistence of the segment (most likely, because it doesn't belong - * to our userid), assume it is in use. */ if (shmctl(shmId, IPC_STAT, &shmStat) < 0) { @@ -233,7 +229,29 @@ PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2) */ if (errno == EINVAL) return false; - /* Else assume segment is in use */ + /* + * EACCES implies that the segment belongs to some other userid, + * which means it is not a Postgres shmem segment (or at least, + * not one that is relevant to our data directory). + */ + if (errno == EACCES) + return false; + /* + * Some Linux kernel versions (in fact, all of them as of July 2007) + * sometimes return EIDRM when EINVAL is correct. The Linux kernel + * actually does not have any internal state that would justify + * returning EIDRM, so we can get away with assuming that EIDRM is + * equivalent to EINVAL on that platform. + */ +#ifdef HAVE_LINUX_EIDRM_BUG + if (errno == EIDRM) + return false; +#endif + /* + * Otherwise, we had better assume that the segment is in use. + * The only likely case is EIDRM, which implies that the segment + * has been IPC_RMID'd but there are still processes attached to it. + */ return true; } /* If it has attached processes, it's in use */ diff --git a/src/include/port/linux.h b/src/include/port/linux.h index 3d00c0aecdc..84da4d1027a 100644 --- a/src/include/port/linux.h +++ b/src/include/port/linux.h @@ -55,3 +55,16 @@ typedef unsigned char slock_t; #define HAS_TEST_AND_SET #endif + +/* + * As of July 2007, all known versions of the Linux kernel will sometimes + * return EIDRM for a shmctl() operation when EINVAL is correct (it happens + * when the low-order 15 bits of the supplied shm ID match the slot number + * assigned to a newer shmem segment). We deal with this by assuming that + * EIDRM means EINVAL in PGSharedMemoryIsInUse(). This is reasonably safe + * since in fact Linux has no excuse for ever returning EIDRM; it doesn't + * track removed segments in a way that would allow distinguishing them from + * private ones. But someday that code might get upgraded, and we'd have + * to have a kernel version test here. + */ +#define HAVE_LINUX_EIDRM_BUG |