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SubjectRe: [PATCH] conditionally reschedule while loading selinux policy.
On Mon, Sep 16, 2013 at 02:40:30PM -0400, Dave Jones wrote:
> On a slow machine (with debugging enabled), upgrading selinux policy may take
> a considerable amount of time. Long enough that the softlockup detector
> gets triggered.
>
> The backtrace looks like this..
>
> > BUG: soft lockup - CPU#2 stuck for 23s! [load_policy:19045]
> > Call Trace:
> > [<ffffffff81221ddf>] symcmp+0xf/0x20
> > [<ffffffff81221c27>] hashtab_search+0x47/0x80
> > [<ffffffff8122e96c>] mls_convert_context+0xdc/0x1c0
> > [<ffffffff812294e8>] convert_context+0x378/0x460
> > [<ffffffff81229170>] ? security_context_to_sid_core+0x240/0x240
> > [<ffffffff812221b5>] sidtab_map+0x45/0x80
> > [<ffffffff8122bb9f>] security_load_policy+0x3ff/0x580

With that patch applied, the problem seems to have moved elsewhere..

BUG: soft lockup - CPU#3 stuck for 22s! [load_policy:8119]
irq event stamp: 1590886
hardirqs last enabled at (1590885): [<ffffffff8152c3dd>] __slab_alloc.constprop.78+0x4c0/0x4d7
hardirqs last disabled at (1590886): [<ffffffff8153e06a>] apic_timer_interrupt+0x6a/0x80
softirqs last enabled at (1590336): [<ffffffff810480d9>] __do_softirq+0x169/0x200
softirqs last disabled at (1590331): [<ffffffff8104839d>] irq_exit+0x11d/0x140
RIP: 0010:[<ffffffff81223182>] [<ffffffff81223182>] hashtab_insert+0x62/0x110

Call Trace:
[<ffffffff812283b5>] policydb_read+0xc25/0x1200
[<ffffffff810b1639>] ? is_module_text_address+0x19/0x40
[<ffffffff8122cefe>] security_load_policy+0x10e/0x580
[<ffffffff81078878>] ? sched_clock_cpu+0xa8/0x100
[<ffffffff810786ad>] ? sched_clock_local+0x1d/0x80
[<ffffffff81078878>] ? sched_clock_cpu+0xa8/0x100
[<ffffffff810786ad>] ? sched_clock_local+0x1d/0x80
[<ffffffff81078878>] ? sched_clock_cpu+0xa8/0x100
[<ffffffff8103098a>] ? __change_page_attr_set_clr+0x82a/0xa50
[<ffffffff81078878>] ? sched_clock_cpu+0xa8/0x100
[<ffffffff8153669c>] ? retint_restore_args+0xe/0xe
[<ffffffff810a196d>] ? trace_hardirqs_on_caller+0xfd/0x1c0
[<ffffffff8127b07e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[<ffffffff810d2958>] ? rcu_irq_exit+0x68/0xb0
[<ffffffff8153669c>] ? retint_restore_args+0xe/0xe
[<ffffffff8121ff97>] sel_write_load+0xa7/0x770
[<ffffffff811394c3>] ? vfs_write+0x1c3/0x200
[<ffffffff812124de>] ? security_file_permission+0x1e/0xa0
[<ffffffff811393bb>] vfs_write+0xbb/0x200
[<ffffffff81158337>] ? fget_light+0x397/0x4b0
[<ffffffff81139ab7>] SyS_write+0x47/0xa0
[<ffffffff8153d634>] tracesys+0xdd/0xe2

We're holding a bunch of locks here, so we can't just cond_resched. Thoughts ?

Dave



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