[lkml]   [2008]   [Jan]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    Patch in this message
    SubjectRe: 2.6.24-rc7 lockdep warning when poweroff

    Ok, I checked all users of the create*workqueue() API now.

    Turns out that there are many users that give a dynamic string as the
    workqueue name (only the first three are relevant for the problem at
    hand because the others are single-threaded):


    drivers/i2c/chips/m41t00.c drivers/infiniband/core/mad.c
    drivers/message/fusion/mptfc.c drivers/net/qla3xxx.c
    drivers/scsi/hosts.c drivers/scsi/qla4xxx/ql4_os.c
    drivers/scsi/scsi_transport_fc.c drivers/spi/mpc52xx_psc_spi.c
    drivers/spi/omap2_mcspi.c drivers/spi/spi_bitbang.c
    drivers/spi/spi_txx9.c drivers/spi/spi_imx.c drivers/spi/pxa2xx_spi.c
    drivers/spi/spi_bfin5xx.c drivers/power/ds2760_battery.c

    That's not really the problem though.

    TBH, when writing the workqueue deadlock detection code I wasn't aware
    that it is not allowed to use the same key with different names.

    To make sure now:
    same key - different name - BAD
    same key - same name - OK
    different key - same name - OK
    different key - different name - OK


    The root problem here seems to be that I use the same name as for the
    workqueue for the lockdep_map and other code uses a non-static workqueue
    name. Using the workqueue name for the lock is good for knowing which
    workqueue ran into trouble though.

    mac80211 for example wants to allocate a (single-threaded) workqueue for
    each hardware that is plugged in and wants to call it by the hardware

    Anyway, the patch below should help. I hope the patch compiles, I don't
    have a lockdep-enabled system at hand right now (irqtrace is still not
    supported on powerpc and my 64-bit powerpc isn't running a kernel with
    my irqtrace support patch at the moment).

    If you think the patch is a correct way to solve the problem I'll submit
    it formally and it should then be included in 2.6.24 to avoid
    regressions with the workqueue API (the workqueue lockup detection was
    merged early in 2.6.24.) Who should I send it to in that case?

    Dave, do you know if you had connector, ivtv or i2o in the kernel (just
    to make sure my analysis was correct)? And can you reproduce the
    problem, and if so, can you try if this patch helps?


    include/linux/workqueue.h | 14 +++++++++++---
    kernel/workqueue.c | 5 +++--
    2 files changed, 14 insertions(+), 5 deletions(-)

    --- everything.orig/include/linux/workqueue.h 2008-01-15 02:10:55.098131131 +0100
    +++ everything/include/linux/workqueue.h 2008-01-15 02:26:37.428130426 +0100
    @@ -149,19 +149,27 @@ struct execute_work {

    extern struct workqueue_struct *
    __create_workqueue_key(const char *name, int singlethread,
    - int freezeable, struct lock_class_key *key);
    + int freezeable, struct lock_class_key *key,
    + const char *lock_name);

    #define __create_workqueue(name, singlethread, freezeable) \
    ({ \
    static struct lock_class_key __key; \
    + const char *__lock_name; \
    + \
    + if (__builtin_constant_p(name)) \
    + __lock_name = (name); \
    + else \
    + __lock_name = #name; \
    __create_workqueue_key((name), (singlethread), \
    - (freezeable), &__key); \
    + (freezeable), &__key, \
    + __lock_name); \
    #define __create_workqueue(name, singlethread, freezeable) \
    - __create_workqueue_key((name), (singlethread), (freezeable), NULL)
    + __create_workqueue_key((name), (singlethread), (freezeable), NULL, NULL)

    #define create_workqueue(name) __create_workqueue((name), 0, 0)
    --- everything.orig/kernel/workqueue.c 2008-01-15 02:15:13.578132867 +0100
    +++ everything/kernel/workqueue.c 2008-01-15 02:18:40.518138455 +0100
    @@ -722,7 +722,8 @@ static void start_workqueue_thread(struc
    struct workqueue_struct *__create_workqueue_key(const char *name,
    int singlethread,
    int freezeable,
    - struct lock_class_key *key)
    + struct lock_class_key *key,
    + const char *lock_name)
    struct workqueue_struct *wq;
    struct cpu_workqueue_struct *cwq;
    @@ -739,7 +740,7 @@ struct workqueue_struct *__create_workqu

    wq->name = name;
    - lockdep_init_map(&wq->lockdep_map, name, key, 0);
    + lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
    wq->singlethread = singlethread;
    wq->freezeable = freezeable;

     \ /
      Last update: 2008-01-15 13:09    [W:0.024 / U:21.720 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site