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* Shared memory shmat/dt not working well in 2.5.x
@ 2002-10-01  9:52 Zlatko Calusic
  2002-10-01 13:07 ` Alessandro Suardi
                   ` (2 more replies)
  0 siblings, 3 replies; 14+ messages in thread
From: Zlatko Calusic @ 2002-10-01  9:52 UTC (permalink / raw)
  To: akpm, hugh; +Cc: linux-kernel

[-- Attachment #1: Type: text/plain, Size: 1594 bytes --]

Hi, Andrew, Hugh & others.

Still having problems with Oracle on 2.5.x (it can't even be started),
I devoted some time trying to pinpoint where the problem is. Reading
many traces of Oracle, and rebooting a dozen times, I finally found
that the culprit is weird behaviour of shmat/shmdt functions in 2.5,
when combined with mprotect() calls. I wrote a simple test app
(attached) and I'm also appending output of it below (running on
2.4.19 & 2.5.39 kernels, see the difference).

Hopefully, somebody will know how to help resolve that issue, so I can
finally benchmark Oracle on 2.4 vs Oracle on 2.5. ;)

Best regards,


{2.4.19} % shm-bug
First shmat & protects done: 50000000
50000000-51000000 rw-s 00000000 00:04 327974932  /SYSV01478e7f (deleted)
51000000-51001000 r--s 01000000 00:04 327974932  /SYSV01478e7f (deleted)
51001000-51081000 rw-s 01001000 00:04 327974932  /SYSV01478e7f (deleted)
51081000-51082000 r--s 01081000 00:04 327974932  /SYSV01478e7f (deleted)
51082000-51083000 rw-s 01082000 00:04 327974932  /SYSV01478e7f (deleted)
Second shmat done: 50000000
50000000-51083000 rw-s 00000000 00:04 327974932  /SYSV01478e7f (deleted)

{2.5.39} % shm-bug
First shmat & protects done: 50000000
50000000-51000000 rw-s 00000000 00:06 2457614    /SYSV01478e7f (deleted)
51000000-51001000 r--s 00000000 00:06 2457614    /SYSV01478e7f (deleted)
51001000-51081000 rw-s 00001000 00:06 2457614    /SYSV01478e7f (deleted)
51081000-51082000 r--s 00001000 00:06 2457614    /SYSV01478e7f (deleted)
51082000-51083000 rw-s 00002000 00:06 2457614    /SYSV01478e7f (deleted)
shmat 2: Invalid argument


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: shm-bug.c --]
[-- Type: text/x-csrc, Size: 1190 bytes --]

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/mman.h>

#define SIZE 17313792

void xperror(char *error_string)
{
	perror(error_string);
	exit(EXIT_FAILURE);
}

int main(int argc, char **argv)
{
	int shmid, *addr;
	char buffer[64];

	if ((shmid = shmget(21466751, SIZE, IPC_CREAT | IPC_EXCL | 0640)) < 0)
		xperror("shmget");
	addr = (int *) shmat(shmid, (char *) 0x50000000, 0);
	if (addr == (int *) -1)
		xperror("shmat 1");
	if (mprotect((char *) 0x51000000, 4096, PROT_READ) < 0)
		xperror("mprotect 1");
	if (mprotect((char *) 0x51081000, 4096, PROT_READ) < 0)
		xperror("mprotect 2");
	printf("First shmat & protects done: %08lx\n", (unsigned long) addr);
	sprintf(buffer, "cat /proc/%d/maps | grep /SYSV", getpid());
	system(buffer);
	if (shmdt(addr) < 0)
		xperror("shmdt 1");
	addr = (int *) shmat(shmid, (char *) 0x50000000, 0);
	if (addr == (int *) -1) {
		perror("shmat 2");
		shmctl(shmid, IPC_RMID, NULL);
		exit(EXIT_FAILURE);
	}
	printf("Second shmat done: %08lx\n", (unsigned long) addr);
	system(buffer);
	if (shmdt(addr) < 0)
		xperror("shmdt 2");
	shmctl(shmid, IPC_RMID, NULL);
	exit(EXIT_SUCCESS);
}

[-- Attachment #3: Type: text/plain, Size: 12 bytes --]


-- 
Zlatko

^ permalink raw reply	[flat|nested] 14+ messages in thread

end of thread, other threads:[~2002-10-08 15:20 UTC | newest]

Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2002-10-01  9:52 Shared memory shmat/dt not working well in 2.5.x Zlatko Calusic
2002-10-01 13:07 ` Alessandro Suardi
2002-10-01 13:09 ` [PATCH] " Hugh Dickins
2002-10-01 13:28   ` Alessandro Suardi
2002-10-01 13:46     ` Zlatko Calusic
2002-10-01 14:51       ` Alessandro Suardi
2002-10-01 14:59         ` Zlatko Calusic
2002-10-02 18:45         ` Zlatko Calusic
2002-10-08 11:22           ` Zlatko Calusic
2002-10-08 11:38             ` Duncan Sands
2002-10-08 15:10               ` Zlatko Calusic
2002-10-08 15:25                 ` Duncan Sands
2002-10-01 13:37   ` Zlatko Calusic
2002-10-01 15:32 ` [PATCH] Oracle startup split_vma fix Hugh Dickins

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