Hi Joachim- Joachim Fenkes wrote: > > idr_init(), when called for the first time, sets up the layer > cache. idr_get_new() and friends expect the cache to exist. Now, what happens > if the first call to idr_get_new() targets an idr initialized using > DEFINE_IDR() before idr_init() has been called at least once? Could this > happen?
unnamed_dev_init() is the first caller of idr_init() and it happens to be called before the first use of idr_get_new(): [ 0.831907] [<c010615a>] dump_stack+0x16/0x18 [ 0.831945] [<c01c2714>] idr_init+0x3c/0x9c [ 0.831985] [<c038cab8>] unnamed_dev_init+0xd/0xf [ 0.832027] [<c037b987>] start_kernel+0x307/0x341 [ 0.832068] [<00000000>] 0x0 [ 0.832149] ======================= [ 0.832881] Mount-cache hash table entries: 512 [ 0.833432] [<c010615a>] dump_stack+0x16/0x18 [ 0.833470] [<c01c298f>] idr_get_new_above_int+0x43/0x222 [ 0.833541] [<c01c2b7b>] idr_get_new+0xd/0x28 [ 0.833605] [<c0169243>] set_anon_super+0x36/0xa0 [ 0.833667] [<c01696be>] sget+0x234/0x2c9 [ 0.833722] [<c016a01e>] get_sb_single+0x24/0x8e [ 0.833781] [<c01a2468>] sysfs_get_sb+0x1c/0x1e [ 0.833867] [<c0169b63>] vfs_kern_mount+0x41/0x70 [ 0.833927] [<c0169ba8>] kern_mount+0x16/0x18 [ 0.833984] [<c038e494>] sysfs_init+0x57/0xa5 [ 0.834026] [<c038cfe3>] mnt_init+0xc5/0x1cb [ 0.834064] [<c038cce8>] vfs_caches_init+0x141/0x152 [ 0.834104] [<c037b996>] start_kernel+0x316/0x341 [ 0.834144] [<00000000>] 0x0 [ 0.834174] ======================= It does seem fragile, though. AFAICT there's no guarantee that a DEFINE_IDR user couldn't call idr_get_new() before unnamed_dev_init() runs. Also, init_id_cache() in idr.c is racy wrt itself. If the first two uses of idr_init() occur concurrently, the code could attempt to create idr_layer_cache twice. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
