Environment: Pre Pentium systems, (boot_cpu_data.wp_works_ok == 0)
Last known working kernel: 2.6.18 (did not try 2.6.19 yet)
Enabling CONFIG_PREEMPT on latest mainline as well as 2.6.20 trigger
[ 14.150000] BUG: sleeping function called from invalid context at
/home/tglx/work/kernel/vanilla/linux-2.6.20/kernel/rwsem.c:20
[ 14.160000] in_atomic():1, irqs_disabled():0
[ 14.160000] no locks held by init/1.
[ 14.170000] [<c0103346>] show_trace_log_lvl+0x1a/0x2f
[ 14.180000] [<c0103441>] show_trace+0x12/0x14
[ 14.190000] [<c0103cf5>] dump_stack+0x16/0x18
[ 14.190000] [<c010aa62>] __might_sleep+0xc7/0xcd
[ 14.200000] [<c01213a1>] down_read+0x18/0x47
[ 14.210000] [<c01a01e4>] __copy_to_user_ll+0x5e/0x1b6
[ 14.220000] [<c012cf85>] file_read_actor+0x10b/0x149
[ 14.230000] [<c012d7b2>] do_generic_mapping_read+0x187/0x433
[ 14.240000] [<c012f64b>] generic_file_aio_read+0x191/0x1ca
[ 14.240000] [<c0141657>] do_sync_read+0xc2/0xff
[ 14.250000] [<c0141eb6>] vfs_read+0x90/0x145
[ 14.260000] [<c014227e>] sys_read+0x3f/0x63
[ 14.270000] [<c0102fb0>] syscall_call+0x7/0xb
[ 14.270000] =======================
and
[ 22.660000] BUG: scheduling while atomic: e2fsck/0x10000001/272
[ 22.670000] 1 lock held by e2fsck/272:
[ 22.680000] #0: (&mm->mmap_sem){----}, at: [<c01a01e4>]
__copy_to_user_ll+0x5e/0x1b6
[ 22.690000] [<c0103346>] show_trace_log_lvl+0x1a/0x2f
[ 22.700000] [<c0103441>] show_trace+0x12/0x14
[ 22.710000] [<c0103cf5>] dump_stack+0x16/0x18
[ 22.720000] [<c024a189>] __sched_text_start+0x71/0x57f
[ 22.720000] [<c010b49f>] __cond_resched+0x21/0x3b
[ 22.730000] [<c024aca7>] cond_resched+0x26/0x31
[ 22.740000] [<c0137ae5>] get_user_pages+0x1e1/0x23c
[ 22.750000] [<c01a021e>] __copy_to_user_ll+0x98/0x1b6
[ 22.760000] [<c012cf85>] file_read_actor+0x10b/0x149
[ 22.770000] [<c012d7b2>] do_generic_mapping_read+0x187/0x433
[ 22.780000] [<c012f64b>] generic_file_aio_read+0x191/0x1ca
[ 22.790000] [<c0141657>] do_sync_read+0xc2/0xff
[ 22.790000] [<c0141eb6>] vfs_read+0x90/0x145
[ 22.800000] [<c014227e>] sys_read+0x3f/0x63
[ 22.810000] [<c0102fb0>] syscall_call+0x7/0xb
[ 22.820000] =======================
which is not surprising.
int file_read_actor(read_descriptor_t *desc, struct page *page,
unsigned long offset, unsigned long size)
{
....
/*
* Faults on the destination of a read are common, so do it before
* taking the kmap.
*/
if (!fault_in_pages_writeable(desc->arg.buf, size)) {
kaddr = kmap_atomic(page, KM_USER0);
----> left = __copy_to_user_inatomic(desc->arg.buf,
kaddr + offset, size);
is called with preempt_count == 1, due to the kmap_atomic() above.
Now __copy_to_user_ll() takes the (boot_cpu_data.wp_works_ok == 0) path,
which in turn calls
down_read(current->mm->mmap_sem) - which might sleep
and
get_user_pages() - which has a cond_resched() inside.
Not sure how to fix that.
tglx
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