From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 5E7ED6B0069 for ; Wed, 16 Nov 2011 00:35:54 -0500 (EST) Received: by bke17 with SMTP id 17so139982bke.14 for ; Tue, 15 Nov 2011 21:35:50 -0800 (PST) MIME-Version: 1.0 Date: Wed, 16 Nov 2011 11:05:49 +0530 Message-ID: Subject: Crash when memset of shared mapped memory in ARM From: naveen yadav Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Russell King - ARM Linux , linux-mm , linux-arm-kernel-request@lists.arm.linux.org.uk, linux-arm-kernel@lists.infradead.org, linux-arm-request@lists.arm.linux.org.uk, linux-kernel@vger.kernel.org Hi All, I am running below Test program on ARM cortex a9/a8 on kernel version 2.6.35.14 as well as on 3.0. Please find the test case where: 1. Create shared memory object using shm_open(If we use normal open then no problem only problem with shm_open) 2. ftruncate to given size 3. memory map the shared object to given memory address ( I haved tested without MAP_SHARED, MAP_FIXED as well, problem exist) 4. Memset the shared memory (got page fault when accessing the second page) Observation: Only observed in ARM ( i.e not present in MIPS and X86) #undef NDEBUG #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include #include #include enum { SHM_INIT, SHM_GET }; enum { PARENT, CHILD }; #define FIXED_MMAP_ADDR 0x20000000 #define MMAP_SIZE 0x10000 static int shmid; static char shm_name[100]; static int sleep_period = 100000; void * shmem_init(int flag) { int start = FIXED_MMAP_ADDR; int memory_size = MMAP_SIZE; int mode = 0666; void *addr; int ret; sprintf(shm_name, "/shmem_1234"); shmid = shm_open (shm_name, O_RDWR | O_EXCL | O_CREAT | O_TRUNC, mode); if (shmid < 0) { if (errno == EEXIST) { printf ("shm_open: %s\n", strerror(errno)); shmid = shm_open (shm_name, O_RDWR, mode); } else { printf("failed to shm_open, err=%s\n", strerror(errno)); return NULL; } } ret = fcntl (shmid, F_SETFD, FD_CLOEXEC); if (ret < 0) { printf("fcntl: %s\n", strerror(errno)); return NULL; } ret = ftruncate (shmid, memory_size); if (ret < 0) { printf("ftruncate: %s\n", strerror(errno)); return NULL; } addr = mmap ((void *)start, memory_size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, shmid, 0); if (addr == MAP_FAILED) { printf ("mmap: %s\n", strerror(errno)); close (shmid); shm_unlink (shm_name); return NULL; } if (flag == SHM_INIT){ printf ("mmap: addr %p\n", addr); /* memset on arm creates a unhandled page fault, works fine on mips */ memset(addr, 0, memory_size); } return (void *)addr; } pthread_mutex_t * shmem_mutex_init(int flag) { pthread_mutex_t * pmutex = (pthread_mutex_t *)shmem_init(flag); #if 0 pthread_mutexattr_t attr; if (flag == SHM_INIT) { pthread_mutexattr_init (&attr); pthread_mutexattr_setpshared (&attr, PTHREAD_PROCESS_SHARED); pthread_mutexattr_setprotocol (&attr, PTHREAD_PRIO_INHERIT); pthread_mutexattr_setrobust_np (&attr, PTHREAD_MUTEX_STALLED_NP); pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ERRORCHECK); if (pthread_mutex_init (pmutex, &attr) != 0) { printf("Init mutex failed, err=%s\n", strerror(errno)); pthread_mutexattr_destroy (&attr); return NULL; } } #endif return pmutex; } void long_running_task(int flag) { static int counter = 0; if (flag == PARENT) usleep(5*sleep_period); else usleep(3*sleep_period); counter = (counter + 1) % 100; printf("%d: completed %d computing\n", getpid(), counter); } void sig_handler(int signum) { close(shmid); shm_unlink(shm_name); exit(0); } int main(int argc, char *argv[]) { pthread_mutex_t *mutex_parent, *mutex_child; // signal(SIGUSR1, sig_handler); // if (fork()) { /* parent process */ if ((mutex_parent = shmem_mutex_init(SHM_INIT)) == NULL) { printf("failed to get the shmem_mutex\n"); exit(-1); } #if 0 while (1) { printf("%d: try to hold the lock\n", getpid()); pthread_mutex_lock(mutex_parent); printf("%d: got the lock\n", getpid()); long_running_task(PARENT); pthread_mutex_unlock(mutex_parent); printf("%d: released the lock\n", getpid()); } #endif // } else { #if 0 /* child process */ usleep(sleep_period); if ((mutex_child = shmem_mutex_init(SHM_GET)) == NULL) { printf("failed to get the shmem_mutex\n"); exit(-1); } while (1) { printf("%d: try to hold the lock\n", getpid()); pthread_mutex_lock(mutex_child); printf("%d: got the lock\n", getpid()); long_running_task(CHILD); pthread_mutex_unlock(mutex_child); printf("%d: released the lock\n", getpid()); } #endif // } return 0; } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org