> On Jan 28, 2019, at 5:21 PM, Alexei Starovoitov <a...@kernel.org> wrote:
>
> From: Peter Zijlstra <pet...@infradead.org>
>
> Introduce cant_sleep() macro for annotation of functions that cannot sleep.
>
> Use it in BPF_PROG_RUN to catch execution of BPF programs
> in preemptable context.
>
> Suggested-by: Jann Horn <ja...@google.com>
> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
> Signed-off-by: Alexei Starovoitov <a...@kernel.org>
Acked-by: Song Liu <songliubrav...@fb.com>
> ---
> include/linux/filter.h | 2 +-
> include/linux/kernel.h | 14 ++++++++++++--
> kernel/sched/core.c | 28 ++++++++++++++++++++++++++++
> 3 files changed, 41 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index e4b473f85b46..7e87863617b3 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -533,7 +533,7 @@ struct sk_filter {
> struct bpf_prog *prog;
> };
>
> -#define BPF_PROG_RUN(filter, ctx) (*(filter)->bpf_func)(ctx,
> (filter)->insnsi)
> +#define BPF_PROG_RUN(filter, ctx) ({ cant_sleep();
> (*(filter)->bpf_func)(ctx, (filter)->insnsi); })
>
> #define BPF_SKB_CB_LEN QDISC_CB_PRIV_LEN
>
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 8f0e68e250a7..a8868a32098c 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -245,8 +245,10 @@ extern int _cond_resched(void);
> #endif
>
> #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
> - void ___might_sleep(const char *file, int line, int preempt_offset);
> - void __might_sleep(const char *file, int line, int preempt_offset);
> +extern void ___might_sleep(const char *file, int line, int preempt_offset);
> +extern void __might_sleep(const char *file, int line, int preempt_offset);
> +extern void __cant_sleep(const char *file, int line, int preempt_offset);
> +
> /**
> * might_sleep - annotation for functions that can sleep
> *
> @@ -259,6 +261,13 @@ extern int _cond_resched(void);
> */
> # define might_sleep() \
> do { __might_sleep(__FILE__, __LINE__, 0); might_resched(); } while (0)
> +/**
> + * cant_sleep - annotation for functions that cannot sleep
> + *
> + * this macro will print a stack trace if it is executed with preemption
> enabled
> + */
> +# define cant_sleep() \
> + do { __cant_sleep(__FILE__, __LINE__, 0); } while (0)
> # define sched_annotate_sleep() (current->task_state_change = 0)
> #else
> static inline void ___might_sleep(const char *file, int line,
> @@ -266,6 +275,7 @@ extern int _cond_resched(void);
> static inline void __might_sleep(const char *file, int line,
> int preempt_offset) { }
> # define might_sleep() do { might_resched(); } while (0)
> +# define cant_sleep() do { } while (0)
> # define sched_annotate_sleep() do { } while (0)
> #endif
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index a674c7db2f29..1dcbff62f973 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6149,6 +6149,34 @@ void ___might_sleep(const char *file, int line, int
> preempt_offset)
> add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
> }
> EXPORT_SYMBOL(___might_sleep);
> +
> +void __cant_sleep(const char *file, int line, int preempt_offset)
> +{
> + static unsigned long prev_jiffy;
> +
> + if (irqs_disabled())
> + return;
> +
> + if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
> + return;
> +
> + if (preempt_count() > preempt_offset)
> + return;
> +
> + if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
> + return;
> + prev_jiffy = jiffies;
> +
> + printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line);
> + printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name:
> %s\n",
> + in_atomic(), irqs_disabled(),
> + current->pid, current->comm);
> +
> + debug_show_held_locks(current);
> + dump_stack();
> + add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
> +}
> +EXPORT_SYMBOL_GPL(__cant_sleep);
> #endif
>
> #ifdef CONFIG_MAGIC_SYSRQ
> --
> 2.20.0
>
