Messages in this thread |  | | From | Dmitry Vyukov <> | Date | Sat, 25 Jul 2020 06:48:21 +0200 | Subject | Re: [PATCH] lockdep: Introduce CONFIG_LOCKDEP_LARGE |
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On Sat, Jul 25, 2020 at 3:30 AM Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> wrote: > > Since syzkaller continues various test cases until the kernel crashes, > syzkaller tends to examine more locking dependencies than normal systems. > As a result, syzbot is reporting that the fuzz testing was terminated > due to hitting upper limits lockdep can track [1] [2] [3]. > > Like CONFIG_LOCKDEP_SMALL which halves the upper limits, let's introduce > CONFIG_LOCKDEP_LARGE which doubles the upper limits. > > [1] https://syzkaller.appspot.com/bug?id=3d97ba93fb3566000c1c59691ea427370d33ea1b > [2] https://syzkaller.appspot.com/bug?id=381cb436fe60dc03d7fd2a092b46d7f09542a72a > [3] https://syzkaller.appspot.com/bug?id=a588183ac34c1437fc0785e8f220e88282e5a29f > > Reported-by: syzbot <syzbot+cd0ec5211ac07c18c049@syzkaller.appspotmail.com> > Reported-by: syzbot <syzbot+91fd909b6e62ebe06131@syzkaller.appspotmail.com> > Reported-by: syzbot <syzbot+62ebe501c1ce9a91f68c@syzkaller.appspotmail.com> > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> > --- > kernel/locking/lockdep.c | 4 ++++ > kernel/locking/lockdep_internals.h | 5 +++++ > lib/Kconfig.debug | 8 ++++++++ > 3 files changed, 17 insertions(+) > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index 29a8de4..85ba7eb 100644 > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -1349,7 +1349,11 @@ static int add_lock_to_list(struct lock_class *this, > /* > * For good efficiency of modular, we use power of 2 > */ > +#ifdef CONFIG_LOCKDEP_LARGE > +#define MAX_CIRCULAR_QUEUE_SIZE 8192UL > +#else > #define MAX_CIRCULAR_QUEUE_SIZE 4096UL
Maybe this number should be the config value? So that we don't ever return here to introduce "VERY_LARGE" :) Also somebody may use it to _reduce_ size of the table for a smaller kernel.
> +#endif > #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1) > > /* > diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h > index baca699..00a3ec3 100644 > --- a/kernel/locking/lockdep_internals.h > +++ b/kernel/locking/lockdep_internals.h > @@ -93,6 +93,11 @@ enum { > #define MAX_LOCKDEP_CHAINS_BITS 15 > #define MAX_STACK_TRACE_ENTRIES 262144UL > #define STACK_TRACE_HASH_SIZE 8192 > +#elif defined(CONFIG_LOCKDEP_LARGE) > +#define MAX_LOCKDEP_ENTRIES 65536UL > +#define MAX_LOCKDEP_CHAINS_BITS 17 > +#define MAX_STACK_TRACE_ENTRIES 1048576UL > +#define STACK_TRACE_HASH_SIZE 32768 > #else > #define MAX_LOCKDEP_ENTRIES 32768UL > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 9ad9210..69ba624 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -1266,6 +1266,14 @@ config LOCKDEP > config LOCKDEP_SMALL > bool > > +config LOCKDEP_LARGE > + bool "Use larger buffer for tracking more locking dependencies" > + depends on LOCKDEP && !LOCKDEP_SMALL > + help > + If you say Y here, the upper limits the lock dependency engine uses will > + be doubled. Useful for fuzz testing which tends to test many complecated > + dependencies than normal systems. > + > config DEBUG_LOCKDEP > bool "Lock dependency engine debugging" > depends on DEBUG_KERNEL && LOCKDEP > -- > 1.8.3.1 >
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