Re: How to shoot yourself in the foot: kill -9 postmaster

From: Peter Eisentraut <peter_e(at)gmx(dot)net>
To: Alfred Perlstein <bright(at)wintelcom(dot)net>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Lamar Owen <lamar(dot)owen(at)wgcr(dot)org>, Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: How to shoot yourself in the foot: kill -9 postmaster
Date: 2001-03-06 19:19:12
Message-ID: Pine.LNX.4.30.0103062011230.778-100000@peter.localdomain
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Alfred Perlstein writes:

> Seriously, there's some dispute on the type that 'shm_nattch' is,
> under Solaris it's "shmatt_t" (unsigned long afaik), under FreeBSD
> it's 'short' (i should fix this. :)).

What I don't like is that my /usr/include/sys/shm.h (through other
headers) has:

typedef unsigned long int shmatt_t;

/* Data structure describing a set of semaphores. */
struct shmid_ds
{
struct ipc_perm shm_perm; /* operation permission struct */
size_t shm_segsz; /* size of segment in bytes */
__time_t shm_atime; /* time of last shmat() */
unsigned long int __unused1;
__time_t shm_dtime; /* time of last shmdt() */
unsigned long int __unused2;
__time_t shm_ctime; /* time of last change by shmctl() */
unsigned long int __unused3;
__pid_t shm_cpid; /* pid of creator */
__pid_t shm_lpid; /* pid of last shmop */
shmatt_t shm_nattch; /* number of current attaches */
unsigned long int __unused4;
unsigned long int __unused5;
};

whereas /usr/src/linux/include/shm.h has:

struct shmid_ds {
struct ipc_perm shm_perm; /* operation perms */
int shm_segsz; /* size of segment (bytes) */
__kernel_time_t shm_atime; /* last attach time */
__kernel_time_t shm_dtime; /* last detach time */
__kernel_time_t shm_ctime; /* last change time */
__kernel_ipc_pid_t shm_cpid; /* pid of creator */
__kernel_ipc_pid_t shm_lpid; /* pid of last operator */
unsigned short shm_nattch; /* no. of current attaches */
unsigned short shm_unused; /* compatibility */
void *shm_unused2; /* ditto - used by DIPC */
void *shm_unused3; /* unused */
};

Not only note the shm_nattch type, but also shm_segsz, and the "unused"
fields in between. I don't know a thing about the Linux kernel sources,
but this doesn't seem right.

--
Peter Eisentraut peter_e(at)gmx(dot)net http://yi.org/peter-e/

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