Hi,
Just please avoid doing that locking nastyness:
function() {
unlock();
}
lock();
if (something)
function();
else
unlock();
For this case its OK, but please avoid that.
On Thu, 27 Jun 2002, Hugh Dickins wrote:
> Martin reported "Bug with shared memory" to LKML 14 May: hang due to
> schedule in truncate_list_pages called from .... shm_destroy holding
> the shm_lock spinlock. shm_destroy needs that lock for shm_rmid, but
> it can be safely unlocked once link from id to shp has been removed.
> Patch against 2.4.19-rc1 or -pre10-ac2, applies at offset to 2.5.24.
>
> --- 2.4.19-rc1/ipc/shm.c Mon Jun 24 19:14:58 2002
> +++ linux/ipc/shm.c Thu Jun 27 19:34:51 2002
> @@ -117,12 +117,14 @@
> *
> * @shp: struct to free
> *
> - * It has to be called with shp and shm_ids.sem locked
> + * It has to be called with shp and shm_ids.sem locked,
> + * but returns with shp unlocked and freed.
> */
> static void shm_destroy (struct shmid_kernel *shp)
> {
> shm_tot -= (shp->shm_segsz + PAGE_SIZE - 1) >> PAGE_SHIFT;
> shm_rmid (shp->id);
> + shm_unlock(shp->id);
> shmem_lock(shp->shm_file, 0);
> fput (shp->shm_file);
> kfree (shp);
> @@ -150,8 +152,8 @@
> if(shp->shm_nattch == 0 &&
> shp->shm_flags & SHM_DEST)
> shm_destroy (shp);
> -
> - shm_unlock(id);
> + else
> + shm_unlock(id);
> up (&shm_ids.sem);
> }
>
> @@ -511,11 +513,9 @@
> shp->shm_flags |= SHM_DEST;
> /* Do not find it any more */
> shp->shm_perm.key = IPC_PRIVATE;
> + shm_unlock(shmid);
> } else
> shm_destroy (shp);
> -
> - /* Unlock */
> - shm_unlock(shmid);
> up(&shm_ids.sem);
> return err;
> }
> @@ -653,7 +653,8 @@
> if(shp->shm_nattch == 0 &&
> shp->shm_flags & SHM_DEST)
> shm_destroy (shp);
> - shm_unlock(shmid);
> + else
> + shm_unlock(shmid);
> up (&shm_ids.sem);
>
> *raddr = (unsigned long) user_addr;
>
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Sun Jun 30 2002 - 22:00:12 EST