From: Vlastimil Babka <vbabka@suse.cz> To: yalin wang <yalin.wang2010@gmail.com>, Steven Rostedt <rostedt@goodmis.org> Cc: Ingo Molnar <mingo@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Ebru Akagunduz <ebru.akagunduz@gmail.com>, Rik van Riel <riel@redhat.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, jmarchan@redhat.com, mgorman@techsingularity.net, willy@linux.intel.com, linux-kernel <linux-kernel@vger.kernel.org>, linux-mm@kvack.org Subject: Re: [PATCH V4] mm: fix kernel crash in khugepaged thread Date: Tue, 17 Nov 2015 08:43:45 +0100 [thread overview] Message-ID: <564ADAB1.9030500@suse.cz> (raw) In-Reply-To: <8582F660-B54A-474B-960E-CD5D0FF6428F@gmail.com> On 17.11.2015 4:58, yalin wang wrote: > >> On Nov 17, 2015, at 10:43, Steven Rostedt <rostedt@goodmis.org> wrote: >> >> On Tue, 17 Nov 2015 10:21:47 +0800 >> yalin wang <yalin.wang2010@gmail.com> wrote: >> >> >> >> Because the print_fmt has nothing to do with the fields. You can have >> as your print_fmt as: >> >> TP_printk("Message = %s", "hello dolly!") >> >> And both userspace and the kernel with process that correctly (if I got >> string processing working in userspace, which I believe I do). The >> string is processed, it's not dependent on TP_STRUCT__entry() unless it >> references a field there. Which can also be used too: >> >> TP_printk("Message = %s", __entry->musical ? "Hello dolly!" : >> "Death Trap!") >> >> userspace will see in the entry: >> >> print_fmt: "Message = %s", REC->musical ? "Hello dolly!" : "Death Trap!" >> >> as long as the field "musical" exists, all is well. >> >> -- Steve > Aha, i see. > Thanks very much for your explanation. > Better print fat is : > TP_printk("mm=%p, scan_pfn=%s, writable=%d, referenced=%d, none_or_zero=%d, status=%s, unmapped=%d", > __entry->mm, > __entry->pfn == (-1UL) ? "(null)" : itoa(buff, __entry->pin, 10), …..) > > is this possible ? I doubt so. Why don't we just do (with %lx): __entry->pfn != -1UL ? __entry->pfn : 0, Status already tells us that it's not a real pfn 0 (which I doubt would be userspace-mapped and thus reachable by khugepaged anyway?). Also it's what some other tracepoints do, see e.g. mm_page class in include/trace/events/kmem.h. > Thanks > > > > > > > >
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From: Vlastimil Babka <vbabka@suse.cz> To: yalin wang <yalin.wang2010@gmail.com>, Steven Rostedt <rostedt@goodmis.org> Cc: Ingo Molnar <mingo@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Ebru Akagunduz <ebru.akagunduz@gmail.com>, Rik van Riel <riel@redhat.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, jmarchan@redhat.com, mgorman@techsingularity.net, willy@linux.intel.com, linux-kernel <linux-kernel@vger.kernel.org>, linux-mm@kvack.org Subject: Re: [PATCH V4] mm: fix kernel crash in khugepaged thread Date: Tue, 17 Nov 2015 08:43:45 +0100 [thread overview] Message-ID: <564ADAB1.9030500@suse.cz> (raw) In-Reply-To: <8582F660-B54A-474B-960E-CD5D0FF6428F@gmail.com> On 17.11.2015 4:58, yalin wang wrote: > >> On Nov 17, 2015, at 10:43, Steven Rostedt <rostedt@goodmis.org> wrote: >> >> On Tue, 17 Nov 2015 10:21:47 +0800 >> yalin wang <yalin.wang2010@gmail.com> wrote: >> >> >> >> Because the print_fmt has nothing to do with the fields. You can have >> as your print_fmt as: >> >> TP_printk("Message = %s", "hello dolly!") >> >> And both userspace and the kernel with process that correctly (if I got >> string processing working in userspace, which I believe I do). The >> string is processed, it's not dependent on TP_STRUCT__entry() unless it >> references a field there. Which can also be used too: >> >> TP_printk("Message = %s", __entry->musical ? "Hello dolly!" : >> "Death Trap!") >> >> userspace will see in the entry: >> >> print_fmt: "Message = %s", REC->musical ? "Hello dolly!" : "Death Trap!" >> >> as long as the field "musical" exists, all is well. >> >> -- Steve > Aha, i see. > Thanks very much for your explanation. > Better print fat is : > TP_printk("mm=%p, scan_pfn=%s, writable=%d, referenced=%d, none_or_zero=%d, status=%s, unmapped=%d", > __entry->mm, > __entry->pfn == (-1UL) ? "(null)" : itoa(buff, __entry->pin, 10), a?|..) > > is this possible ? I doubt so. Why don't we just do (with %lx): __entry->pfn != -1UL ? __entry->pfn : 0, Status already tells us that it's not a real pfn 0 (which I doubt would be userspace-mapped and thus reachable by khugepaged anyway?). Also it's what some other tracepoints do, see e.g. mm_page class in include/trace/events/kmem.h. > Thanks > > > > > > > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2015-11-17 7:43 UTC|newest] Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-11-12 8:21 [PATCH V4] mm: fix kernel crash in khugepaged thread yalin wang 2015-11-12 8:21 ` yalin wang 2015-11-12 14:29 ` Steven Rostedt 2015-11-12 14:29 ` Steven Rostedt 2015-11-13 10:47 ` Vlastimil Babka 2015-11-13 10:47 ` Vlastimil Babka 2015-11-13 11:54 ` yalin wang 2015-11-13 11:54 ` yalin wang 2015-11-13 14:01 ` Steven Rostedt 2015-11-13 14:01 ` Steven Rostedt 2015-11-16 1:35 ` yalin wang 2015-11-16 1:35 ` yalin wang 2015-11-16 10:16 ` Vlastimil Babka 2015-11-16 10:16 ` Vlastimil Babka 2015-11-16 14:25 ` Steven Rostedt 2015-11-16 14:25 ` Steven Rostedt 2015-11-17 2:21 ` yalin wang 2015-11-17 2:21 ` yalin wang 2015-11-17 2:43 ` Steven Rostedt 2015-11-17 2:43 ` Steven Rostedt 2015-11-17 3:58 ` yalin wang 2015-11-17 3:58 ` yalin wang 2015-11-17 7:43 ` Vlastimil Babka [this message] 2015-11-17 7:43 ` Vlastimil Babka 2015-11-16 14:22 ` Steven Rostedt 2015-11-16 14:22 ` Steven Rostedt 2015-11-13 8:41 Hillf Danton 2015-11-13 8:41 ` Hillf Danton 2015-11-13 10:24 ` yalin wang 2015-11-13 10:24 ` yalin wang
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