Re: [REGRESSION] RLIMIT_DATA crashes named

[Konstantin Khlebnikov <koct9i@gmail.com>]

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On Sat, Sep 17, 2016 at 3:20 PM, Cyrill Gorcunov <gorcunov@gmail.com> wrote:
> On Sat, Sep 17, 2016 at 03:09:09PM +0300, Konstantin Khlebnikov wrote:
>> >
>> > Seems I don't understand the bottom unlikely...
>>
>> This is gcc extrension:  https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html
>> Here macro works as a function which returns bool
>
> no, no, I know for what unlikely extension stand for.
> it was just hard to obtain from without the context.
> this extension implies someone calls for
> if (printk_periodic()) right?

Yep.


Here is perfect macro for that jiffies check: time_in_range_open.

/*
 * Calculate whether a is in the range of [b, c).
 */
#define time_in_range_open(a,b,c) \
(time_after_eq(a,b) && \
time_before(a,c))

So... better version looks like

#define printk_periodic(period, fmt, ...)
({
        static unsigned long __prev __read_mostly = INITIAL_JIFFIES - (period);
        unsigned long __now = jiffies;
        bool __print = !time_in_range_open(__now, __prev, __prev + (period));

        if (__print) {
                __prev = __now;
                printk(fmt, ##__VA_ARGS__);
        }
        unlikely(__print);
})

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printk: add pr_warn_once_per_minute

From: Konstantin Khlebnikov <koct9i@gmail.com>

Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
---
 include/linux/printk.h |   17 +++++++++++++++++
 mm/mmap.c              |    2 +-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 696a56be7d3e..372984b6645b 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -341,11 +341,25 @@ extern asmlinkage void dump_stack(void) __cold;
 	}							\
 	unlikely(__ret_print_once);				\
 })
+#define printk_periodic(period, fmt, ...)			\
+({								\
+	static unsigned long __prev __read_mostly = INITIAL_JIFFIES - (period); \
+	unsigned long __now = jiffies;				\
+	bool __print = !time_in_range_open(__now, __prev, __prev + (period)); \
+								\
+	if (__print) {						\
+		__prev = __now;					\
+		printk(fmt, ##__VA_ARGS__);			\
+	}							\
+	unlikely(__print);					\
+})
 #else
 #define printk_once(fmt, ...)					\
 	no_printk(fmt, ##__VA_ARGS__)
 #define printk_deferred_once(fmt, ...)				\
 	no_printk(fmt, ##__VA_ARGS__)
+#define printk_periodic(period, fmt, ...)			\
+	no_printk(fmt, ##__VA_ARGS__)
 #endif
 
 #define pr_emerg_once(fmt, ...)					\
@@ -365,6 +379,9 @@ extern asmlinkage void dump_stack(void) __cold;
 #define pr_cont_once(fmt, ...)					\
 	printk_once(KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
 
+#define pr_warn_once_per_minute(fmt, ...)			\
+	printk_periodic(HZ * 60, KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
+
 #if defined(DEBUG)
 #define pr_devel_once(fmt, ...)					\
 	printk_once(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
diff --git a/mm/mmap.c b/mm/mmap.c
index ca9d91bca0d6..34f9fb2adcab 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2935,7 +2935,7 @@ bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
 		    mm->data_vm + npages <= rlimit_max(RLIMIT_DATA) >> PAGE_SHIFT)
 			return true;
 		if (!ignore_rlimit_data) {
-			pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Update limits or use boot option ignore_rlimit_data.\n",
+			pr_warn_once_per_minute("%s (%d): VmData %lu exceed data ulimit %lu. Update limits or use boot option ignore_rlimit_data.\n",
 				     current->comm, current->pid,
 				     (mm->data_vm + npages) << PAGE_SHIFT,
 				     rlimit(RLIMIT_DATA));