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Theodore Ts'o: Linux 2.4 Status

Aug 09, 2000, 07:20 (15 Talkback[s])
(Other stories by Theodore Ts'o)


Re-Imagining Linux Platforms to Meet the Needs of Cloud Service Providers

Date: Wed, 9 Aug 2000 01:33:36 -0400
From: Theodore Ts'o tytso@mit.edu
To: linux-kernel@vger.rutgers.edu
Subject: Linux 2.4 Status

Here's the latest Linux 2.4 Status page, which can also be found at


I try to stay current with linux-kernel, but I don't always catch
everything.  If you've reported a problem which has since been fixed,
and it's still on this list, please let me know.

                                                - Ted

                         Linux 2.4 Status/TODO Page

   Last modified: [tytso:20000809.0128EDT]

Should Be Fixed (Confirmation Wanted)

     * Floppy driver broken by VFS changes. Other drivers may be too
       (Stuff gets called after _close now - unload race possibly too)
     * Fbcon races

Capable Of Corrupting Your FS

     * Use PCI DMA by default in IDE is unsafe (must not do so on via
       VPx, x > 3) (requires chipset tuning to be enabled according to
       Andre Hedrick)
     * Data corruption on IDE disks (Generic PCI DMA and SiS support
       (Steven Walter) (possible if BIOS fails on setup)


     * Fix module remove race bug (still to be done: TTY, ldisc, I2C,
       video_device, network devices(?) - Al Viro) (OSS also needs to be
       fixed -- Christoph Hellwig will supply patch)

Boot Time Failures

     * AHA29xx driver appears to stomp other cards (may be BIOS)
     * AHA27xx is broken (maybe 28xx too)
     * Use PCI DMA 'lost interrupt' problem with some hw [which ?] (NEC
       Versa LX with PIIX tuning)
     * HT6560/UMC8672 ide sets up stuff too early (before region stuff
       can be done)
     * Crashes on boot on some Compaqs ? (may be fixed)
     * Boot hangs on a range of Dell docking stations (Latitude)
          + Almost certainly related: PCI code doesn't see devices behind
            DECchip 21150 PCI bridges (used in Dell Latitude). Reported
            by Simon Trimmer .

In Progress

     * Merge the network fixes (DaveM)
     * Finish I2O merge (Intel/Alan)
     * Restore O_SYNC functionality (Stephen) - core code and ext2 done
     * Fix all remaining PCI code to use pci_enable_device (mostly done)

Obvious Projects For People (well if you have the hardware..)

     * nNCR5380 isnt smp safe
     * DMFE is not SMP safe
     * Make syncppp use new ppp code
     * Fix SPX socket code
     * Merge the 2.2 ServeRAID driver into 2.4

Fix Exists But Isnt Merged

     * Update SGI VisWS to new-style IRQ handling (Ingo)
     * Support MP table above 1Gig (Ingo)
     * Dont panic on boot when meeting HP boxes with wacked APIC table
       numbering (AC)
     * Scheduler bugs in RT (Dimitris)
     * HFS is still broken
     * AIC7xxx doesnt work non PCI ? (Doug says OK, new version due
     * Fix boards with different TSC per CPU and kill TSC use on them
     * Floppy last block cache flush error
     * PPC-specific: won't boot on 601 CPU's (powermac) (Andreas Tobler
     * IRDA fixes (patches from Russell King sent to Linus and DAG)>
          + IRDA calls get_random_bytes before random is set up
          + Infinite loop in IrDA parameter code
          + Device name in /proc/net/irda/irias is not updated when
            /proc/sys/net/irda/devname is written
          + IrDA Discovery slot allocation is not random

Compatibility Errors

     * Xterm broke in 2.3.99pre6 (FIONREAD/select loop)

To Do

     * Check all devices use resources properly
     * Tulip hang on rmmod/crashes sometimes
     * Devfs races (mostly done - Al Viro)
     * Fix further NFS races (Al Viro)
     * Test other file systems on write
     * Audit all char and block drivers to ensure they are safe with the
       2.3 locking - a lot of them are not especially on the
       read()/write() path.
     * Keyboard/mouse problems (may be fixed ?)
     * Fix mount failures due to copy_* user mishandling
     * Check all file systems are either LFS compliant or error large
     * Issue with notifiers that try to deregister themselves? (lnz;
       notifier locking change by Garzik should backed out, according to
     * Mount of new fs over existing mointpoint should return an error
       unless forced (Andrew McNabb, Alan Cox)
     * Kernel build has race conditions when building modversions.h
       (Mikael Pettersson)
     * Misc locking problems
          + drivers/pcmcia/ds.c: ds_read & ds_write. SMP locks are
            missing, on UP the sleep_on() use is unsafe.
          + drivers/usb/*.c
               o unsafe sleep_on users
               o usbpl_{read,write}(): on UP concurrent read/write
                 operations could corrupt the urb structures if
                 copy_to_user sleeps, on SMP it's worse.
               o do_execve (Al Viro, reported by Manfred)
               o misc ext2 races

To Do But Non Showstopper

     * Finish 64bit vfs merges (lockf64 and friends missing -- willy?)
     * Go through as 2.4pre kicks in and figure what we should mark
       obsolete for the final 2.4 (i.e. XT hard disk support?)
     * Union mount (Al Viro)
     * Per Process rtsigio limit
     * iget abuse in knfsd
     * Some people report 2.3.x serial problems
     * USB hangs on APM suspend on some machines
     * ISAPnP IRQ handling failing on SB1000 + resource handling bug
     * DVD-RAM is apparently not working for write currently (Rogier
     * Parallel ports should set SA_SHIRQ if PCI (eg in Plip)
     * Devfs compiled in but not mounted causes crap for ->mnt_devname of
       root (Al Viro)
     * PCMCIA/Cardbus hangs (Basically unusable - Hinds pcmcia code is
          + PCMCIA crashes on unloading pci_socket
     * Loop device hangs (Peter Enderborg can duplicate by writing large
       file to dosfs mounted via loop device; Steve Dodd reports deadlock
     * RTL 8139 cards sometimes stop responding. Both drivers don't
       handle this quite good enough yet. (reported by Rogier Wolff)

To Check

     * Check O_APPEND atomicity bug fixing is complete
     * Protection on i_size (sct) [Al Viro mostly done]
     * Mikulas claims we need to fix the getblk/mark_buffer_uptodate
       thing for 2.3.x as well
     * Network block device seems broken by block device changes
     * VFS?VM - mmap/write deadlock (demo code seems to show lock is
     * kiobuf seperate lock functions/bounce/page_address fixes
     * Fix routing by fwmark
     * rw semaphores on inodes to fix read/truncate races ? [Probably
     * Not all device drivers are safe now the write inode lock isnt
       taken on write
     * Multiwrite IDE breaks on a disk error [minor issue at best]
       (hopefully fixed)
     * ACPI/APM suspend issue - IDE related stuff ? (requires full
       taskfile support that was vetoed by Linus)
     * NFS bugs are fixed
     * Chase reports of SMB not working
     * Some AWE cards are not being found by ISAPnP ??
     * SHM segments not always being detached and destroyed right ?
     * RAM disk contents vanishing on cramfs (block change) and bforget
     * ACPI hangs on boot for some systems (Are there any cases left ?)
     * Disappointing performance of Software Raid, esp. write performance
       (reported by Nils Rennebarth)

Drivers In 2.2 not 2.4

Probably Post 2.4

     * per super block write_super needs an async flag
     * addres_space needs a VM pressure/flush callback (Ingo)
     * per file_op rw_kiovec
     * rw sempahores on page faults (mmap_sem) (Currently protected by


     * Incredibly slow loopback tcp bug (believed fixed about 2.3.48)
     * COMX series WAN now merged
     * VM needs rebalancing or we have a bad leak
     * SHM works chroot
     * SHM back compatibility
     * Intel i960 problems with I2O
     * Symbol clashes and other mess from _three_ copies of zlib!
     * PCI buffer overruns
     * Shared memory changes change the API breaking applications (eg
     * Finish softnet driver port over and cleanups
     * via rhine oopses under load ?
     * SCSI generic driver crashes controllers (need to pass
     * UMSDOS fixups resync (not quite done)
     * Make NTFS sort of work
     * Any user can crash FAT fs code with ftruncate
     * AFFS fixups
     * Directory race fix for UFS
     * Security holes in execve()
     * Lan Media WAN update for 2.3
     * Get the Emu10K merged
     * Paride seems to need fixes for the block changes yet
     * Kernel corrupts fs and gs in some situations (Ulrich has demo
     * 1.07 AMI MegaRAID
     * Merge 2.2.15 changes (Alan)
     * Get RAID 0.90 in (Ingo)
     * S/390 Merge
     * NFS DoS fix (security)
     * Merge the RIO driver
     * Fix Space.c duplicate string/write to constants
     * Elevator and block handling queue change errors are all sorted
     * Make sure all drivers return 1 from their __setup functions (Done
     * Enhanced disk statistics
     * Complete vfsmount merge (Al Viro)
     * Merge removed-buf-open directory stuff into VFS (Al Viro)
     * Problems with ip autoconfig according to Zaitcev
     * NFS causes dup kmem_create on reload (Trond)
     * vmalloc(GFP_DMA) is needed for DMA drivers (Ingo)
     * TLB flush should use highest priority (Ingo)
     * SMP affinity code creates multiple dirs with the same name (Ingo)
     * Set SMP affinity mask to actual cpu online mask (needed for some
       boards) (Ingo)
     * heavy swapping corrupts ptes (believed so)
     * pci_set_master forces a 64 latency on low latency setting
       devices.Some boards require all cards have latency <= 32
     * msync fails on NFS (probably fixed anyway)
     * Find out what has ruined disk I/O throughput. (mostly)
     * The netdev name changing stuff broke GRE
     * put_user is broken for i386 machines (security) - sem stuff may be
       wrong too
     * BusLogic crashes when you cat /proc/scsi/BusLogic/0 (Robert de
     * Finish sorting out VM balancing (Rik Van Riel, Juan Quintela et
     * Fix eth= command line
     * 8139 + bridging fails
     * RtSig limit handling bug
     * Signals leak kernel memory (security) [FIX in ac tree]
     * TTY and N_HDLC layer called poll_wait twice per fd and corrupt
     * ATM layer calls poll_wait twice per fd and corrupts memory
     * Random calls poll_wait twice per fd and corrupts memory
     * PCI sound calls poll_wait twice per fd and corrupts memory
     * sbus audio calls poll_wait twice per fd and corrupts memory
     * IBM MCA driver breaks on Device_Inquiry at boot
     * SHM code corrupts memory (Russell)
     * Linux sends a 1K buffer with SCSI inquiries. The ANSI-SCSI limit
       is 255.
     * Linux uses TEST_UNIT_READY to chck for device presence on a
       PUN/LUN. The INQUIRY is the only valid test allowed by the spec.
     * truncate_inode_pages does unsafe page cache operations
     * Fix the ptrace code to be back compatible and add a new PTRACE
       call set for getting the PIII extra registers
     * EPIC100 fixes
     * Tlan and Epic100 crash under load
     * Fix hpfs_unlink (Al Viro)
     * exec loader permissions
     * Locking on getcwd
     * E820 memory setup causes crashes/corruption on some laptops[**VERY
       NASTY**] (fixed in test5)
     * Debian report that the gcc 2.95 possibly miscompiles fault.c or
       mm/remap.c (Perl script available from Arjan) (fixed in test2 or
     * Dcache threading (Al Viro)
     * Sockfs races (removing NULL ->i_sb stuf) (Al Viro)
     * Module remove race bug (done: anything with file_operations, fb
       stuff, procfs stuff - Al Viro)
     * DEFXX driver appears broken (reported fixed by Jeff Garzik)
     * Some FB drivers check the A000 area and find it busy then bomb out
       (checked and fixed, reported by Jeff Garzik)
     * Stick lock_kernel() calls around OSS driver with issues to hard to
       fix nicely for 2.4 itself (Alan, fixed)
     * Merge the current Compaq RAID driver into 2.4 (fixed, reported by
     * mount crashes on Alpha platforms (fixed, reported by Thorsten
     * IDE fails on some VIA boards (eg the i-opener) (reported fixed by
       Konrad Stepien)
     * access_process_mm oops/lockup if task->mm changes (Manfred) [user
       can cause deliberately]
     * PCMCIA IRQ routing should now be fixed modulo ISA cards and bios
       doesn't tell us that an IRQ is ISA-only (Martin Mares)
     * TB Multisound driver hasnt been updated for new isa I/O totally.
       (reported fixed by John Coiner; see
     * yenta (PCMCIA) and pci_socket modules have mutual dependency
       (cardbus_register, yenta_operations) (test5, worked in test3)
       (reported fixed by Erik Mouw)