On Fri, Nov 12, 2010 at 4:36 PM, heechul Yun <heec...@illinois.edu> wrote:
>
>
> On Fri, Nov 12, 2010 at 8:41 AM, stephane eranian <eran...@googlemail.com>
> wrote:
>>
>> On Fri, Nov 12, 2010 at 2:22 PM, heechul Yun <heec...@illinois.edu> wrote:
>> > It was because of a bug in kernel/perf_event.c as shown in the
>> > following.
>> > static int perf_event_period(struct perf_event *event, u64 __user *arg)
>> > {
>> > ...
>> > size = copy_from_user(&value, arg, sizeof(value));
>> > if (size != sizeof(value)) // <--------- bug. should be: if (size)
>> > return
>> > -EFAULT
>> > return -EFAULT;
>> >
>>
>> Ok, I will post a file for this on LKML.
>> Unless you want to do it.
>>
>
> It seems that it is already fixed in the latest 2.6.36 release. All pre
> 2.6.36 (2.6.35 - 2.6.32 at least) had the bug.
That sounds familiar. Yes, now I remember seeing a fix about copy_from_user().
Thanks for tracking this down on your side anyway.
> Heechul
>
>> > I found this bug has been there in all versions before it was finally
>> > fixed
>> > in 2.6.36.
>> > Heechul
>> >
>> > On Thu, Nov 11, 2010 at 9:23 PM, heechul Yun <heec...@illinois.edu>
>> > wrote:
>> >>
>> >> Hi,
>> >> I wanted to adjust sampling period using PERF_EVENT_IOC_PERIOD ioctl.
>> >> I modified the notify_group to change the period at runtime as follows.
>> >> diff --git a/perf_examples/notify_group.c
>> >> b/perf_examples/notify_group.c
>> >> index 76869b0..d8ff5e1 100644
>> >> --- a/perf_examples/notify_group.c
>> >> +++ b/perf_examples/notify_group.c
>> >> @@ -54,6 +54,7 @@ sigio_handler(int n, struct siginfo *info, struct
>> >> sigcontext *sc)
>> >> struct perf_event_mmap_page *hdr;
>> >> struct perf_event_header ehdr;
>> >> uint64_t ip;
>> >> + uint64_t new_period;
>> >> int id, ret;
>> >>
>> >> id = perf_fd2event(fds, num_fds, info->si_fd);
>> >> @@ -87,6 +88,11 @@ skip:
>> >> /*
>> >> * rearm the counter for one more shot
>> >> */
>> >> + new_period = SMPL_PERIOD * 2 ;
>> >> + ret = ioctl(info->si_fd, PERF_EVENT_IOC_PERIOD, new_period);
>> >> + if (ret == -1)
>> >> + err(1, "cannot set");
>> >> +
>> >> ret = ioctl(info->si_fd, PERF_EVENT_IOC_REFRESH, 1);
>> >> if (ret == -1)
>> >> err(1, "cannot refresh");
>> >> It, however, failed to do so as belows.
>> >> $ ./notify_group
>> >> i=0 disabled=0
>> >> i=1 disabled=1
>> >> i=2 disabled=1
>> >> Notification 1: 0x8048f63 fd=3 PERF_COUNT_HW_CPU_CYCLES
>> >> notify_group: cannot set: Invalid argument
>> >>
>> >> Any idea?
>> >>
>> >> BTW, I found an error in perf_event.h of libpfm4 which prevents
>> >> compiling
>> >> the code.
>> >> The following diff is the fix.
>> >> diff --git a/include/perfmon/perf_event.h
>> >> b/include/perfmon/perf_event.h
>> >> index cfddef0..7f2889e 100644
>> >> --- a/include/perfmon/perf_event.h
>> >> +++ b/include/perfmon/perf_event.h
>> >> @@ -13,7 +13,7 @@
>> >> */
>> >> #ifndef _LINUX_PERF_EVENT_H
>> >> #define _LINUX_PERF_EVENT_H
>> >> -
>> >> +#include <linux/types.h>
>> >> #include <sys/types.h>
>> >> #include <inttypes.h>
>> >> #ifndef PR_TASK_PERF_EVENTS_DISABLE
>> >> @@ -236,7 +236,7 @@ typedef struct perf_event_attr {
>> >> #define PERF_EVENT_IOC_DISABLE _IO ('$', 1)
>> >> #define PERF_EVENT_IOC_REFRESH _IO ('$', 2)
>> >> #define PERF_EVENT_IOC_RESET _IO ('$', 3)
>> >> -#define PERF_EVENT_IOC_PERIOD _IOW('$', 4, u64)
>> >> +#define PERF_EVENT_IOC_PERIOD _IOW('$', 4, __u64)
>> >> #define PERF_EVENT_IOC_SET_OUTPUT _IO ('$', 5)
>> >> #define PERF_EVENT_IOC_SET_FILTER _IOW('$', 6, char *)
>> >>
>> >>
>> >> - Heechul
>> >
>> >
>> >
>> > ------------------------------------------------------------------------------
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>> > https://lists.sourceforge.net/lists/listinfo/perfmon2-devel
>> >
>> >
>
>
------------------------------------------------------------------------------
Centralized Desktop Delivery: Dell and VMware Reference Architecture
Simplifying enterprise desktop deployment and management using
Dell EqualLogic storage and VMware View: A highly scalable, end-to-end
client virtualization framework. Read more!
http://p.sf.net/sfu/dell-eql-dev2dev
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