forked from luck/tmp_suning_uos_patched
91f4ab056d
This patch fixes a deadlock problem of the m32r SMP kernel. In the m32r kernel, sys_tas() system call is provided as a test-and-set function for userspace, for backward compatibility. In some multi-threading application program, deadlocks were rarely caused at sys_tas() funcion. Such a deadlock was caused due to a collision of __pthread_lock() and __pthread_unlock() operations. The "tas" syscall is repeatedly called by pthread_mutex_lock() to get a lock, while a lock variable's value is not 0. On the other hand, pthead_mutex_unlock() sets the lock variable to 0 for unlocking. In the previous implementation of sys_tas() routine, there was a possibility that a unlock operation was ignored in the following case: - Assume a lock variable (*addr) was equal to 1 before sys_tas() execution. - __pthread_unlock() operation is executed by the other processor and the lock variable (*addr) is set to 0, between a read operation ("oldval = *addr;") and the following write operation ("*addr = 1;") during a execution of sys_tas(). In this case, the following write operation ("*addr = 1;") overwrites the __pthread_unlock() result, and sys_tas() fails to get a lock in the next turn and after that. According to the attatched patch, sys_tas() returns 0 value in the next turn and deadlocks never happen. Signed-off-by: Hitoshi Yamamoto <Yamamoto.Hitoshi@ap.MitsubishiElectric.co.jp> Signed-off-by: Hirokazu Takata <takata@linux-m32r.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
220 lines
4.7 KiB
C
220 lines
4.7 KiB
C
/*
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* linux/arch/m32r/kernel/sys_m32r.c
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*
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* This file contains various random system calls that
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* have a non-standard calling sequence on the Linux/M32R platform.
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*
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* Taken from i386 version.
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*/
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#include <linux/config.h>
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#include <linux/errno.h>
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <linux/smp.h>
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#include <linux/smp_lock.h>
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#include <linux/sem.h>
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#include <linux/msg.h>
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#include <linux/shm.h>
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#include <linux/stat.h>
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#include <linux/syscalls.h>
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#include <linux/mman.h>
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#include <linux/file.h>
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#include <linux/utsname.h>
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#include <asm/uaccess.h>
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#include <asm/cachectl.h>
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#include <asm/cacheflush.h>
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#include <asm/ipc.h>
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/*
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* sys_tas() - test-and-set
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* linuxthreads testing version
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*/
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#ifndef CONFIG_SMP
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asmlinkage int sys_tas(int *addr)
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{
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int oldval;
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unsigned long flags;
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if (!access_ok(VERIFY_WRITE, addr, sizeof (int)))
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return -EFAULT;
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local_irq_save(flags);
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oldval = *addr;
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if (!oldval)
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*addr = 1;
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local_irq_restore(flags);
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return oldval;
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}
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#else /* CONFIG_SMP */
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#include <linux/spinlock.h>
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static DEFINE_SPINLOCK(tas_lock);
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asmlinkage int sys_tas(int *addr)
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{
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int oldval;
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if (!access_ok(VERIFY_WRITE, addr, sizeof (int)))
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return -EFAULT;
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_raw_spin_lock(&tas_lock);
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oldval = *addr;
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if (!oldval)
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*addr = 1;
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_raw_spin_unlock(&tas_lock);
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return oldval;
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}
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#endif /* CONFIG_SMP */
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/*
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* sys_pipe() is the normal C calling standard for creating
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* a pipe. It's not the way Unix traditionally does this, though.
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*/
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asmlinkage int
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sys_pipe(unsigned long r0, unsigned long r1, unsigned long r2,
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unsigned long r3, unsigned long r4, unsigned long r5,
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unsigned long r6, struct pt_regs regs)
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{
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int fd[2];
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int error;
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error = do_pipe(fd);
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if (!error) {
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if (copy_to_user((void *)r0, (void *)fd, 2*sizeof(int)))
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error = -EFAULT;
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}
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return error;
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}
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asmlinkage long sys_mmap2(unsigned long addr, unsigned long len,
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unsigned long prot, unsigned long flags,
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unsigned long fd, unsigned long pgoff)
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{
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int error = -EBADF;
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struct file *file = NULL;
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flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
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if (!(flags & MAP_ANONYMOUS)) {
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file = fget(fd);
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if (!file)
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goto out;
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}
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down_write(¤t->mm->mmap_sem);
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error = do_mmap_pgoff(file, addr, len, prot, flags, pgoff);
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up_write(¤t->mm->mmap_sem);
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if (file)
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fput(file);
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out:
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return error;
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}
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/*
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* sys_ipc() is the de-multiplexer for the SysV IPC calls..
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*
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* This is really horribly ugly.
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*/
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asmlinkage int sys_ipc(uint call, int first, int second,
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int third, void __user *ptr, long fifth)
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{
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int version, ret;
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version = call >> 16; /* hack for backward compatibility */
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call &= 0xffff;
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switch (call) {
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case SEMOP:
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return sys_semtimedop(first, (struct sembuf __user *)ptr,
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second, NULL);
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case SEMTIMEDOP:
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return sys_semtimedop(first, (struct sembuf __user *)ptr,
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second, (const struct timespec __user *)fifth);
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case SEMGET:
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return sys_semget (first, second, third);
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case SEMCTL: {
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union semun fourth;
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if (!ptr)
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return -EINVAL;
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if (get_user(fourth.__pad, (void __user * __user *) ptr))
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return -EFAULT;
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return sys_semctl (first, second, third, fourth);
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}
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case MSGSND:
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return sys_msgsnd (first, (struct msgbuf __user *) ptr,
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second, third);
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case MSGRCV:
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switch (version) {
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case 0: {
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struct ipc_kludge tmp;
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if (!ptr)
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return -EINVAL;
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if (copy_from_user(&tmp,
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(struct ipc_kludge __user *) ptr,
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sizeof (tmp)))
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return -EFAULT;
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return sys_msgrcv (first, tmp.msgp, second,
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tmp.msgtyp, third);
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}
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default:
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return sys_msgrcv (first,
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(struct msgbuf __user *) ptr,
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second, fifth, third);
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}
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case MSGGET:
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return sys_msgget ((key_t) first, second);
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case MSGCTL:
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return sys_msgctl (first, second,
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(struct msqid_ds __user *) ptr);
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case SHMAT: {
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ulong raddr;
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if (!access_ok(VERIFY_WRITE, (ulong __user *) third,
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sizeof(ulong)))
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return -EFAULT;
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ret = do_shmat (first, (char __user *) ptr, second, &raddr);
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if (ret)
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return ret;
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return put_user (raddr, (ulong __user *) third);
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}
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case SHMDT:
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return sys_shmdt ((char __user *)ptr);
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case SHMGET:
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return sys_shmget (first, second, third);
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case SHMCTL:
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return sys_shmctl (first, second,
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(struct shmid_ds __user *) ptr);
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default:
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return -ENOSYS;
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}
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}
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asmlinkage int sys_uname(struct old_utsname * name)
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{
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int err;
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if (!name)
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return -EFAULT;
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down_read(&uts_sem);
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err=copy_to_user(name, &system_utsname, sizeof (*name));
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up_read(&uts_sem);
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return err?-EFAULT:0;
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}
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asmlinkage int sys_cacheflush(void *addr, int bytes, int cache)
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{
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/* This should flush more selectivly ... */
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_flush_cache_all();
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return 0;
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}
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asmlinkage int sys_cachectl(char *addr, int nbytes, int op)
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{
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/* Not implemented yet. */
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return -ENOSYS;
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}
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