* RE: gettimeofday with interrupts disabled
@ 2006-05-08 17:28 Stone, Joshua I
2006-05-08 22:12 ` James Dickens
0 siblings, 1 reply; 5+ messages in thread
From: Stone, Joshua I @ 2006-05-08 17:28 UTC (permalink / raw)
To: azizeker; +Cc: systemtap
On Sunday, May 07, 2006 6:24 PM, Aziz Eker wrote:
> I want to get some measurements about the time scheduler_tick()
> function takes. To do that, I am finding time difference between the
> start and end of the function using 'gettimeofday_us'. However, the
> scheduler_tick() function is called with interrupts disabled. Does
> 'gettimeofday' continue to run even when interrupts are disabled? If
> not, is there anyway to count the RTC in systemtap?
Calling gettimeofday is only a problem for probes in code sections that
hold a write lock on xtime_lock. See bug #2525 for more details:
http://sources.redhat.com/bugzilla/show_bug.cgi?id=2525
Josh
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: gettimeofday with interrupts disabled
2006-05-08 17:28 gettimeofday with interrupts disabled Stone, Joshua I
@ 2006-05-08 22:12 ` James Dickens
0 siblings, 0 replies; 5+ messages in thread
From: James Dickens @ 2006-05-08 22:12 UTC (permalink / raw)
To: Stone, Joshua I; +Cc: azizeker, systemtap
On 5/8/06, Stone, Joshua I <joshua.i.stone@intel.com> wrote:
> On Sunday, May 07, 2006 6:24 PM, Aziz Eker wrote:
> > I want to get some measurements about the time scheduler_tick()
> > function takes. To do that, I am finding time difference between the
> > start and end of the function using 'gettimeofday_us'. However, the
> > scheduler_tick() function is called with interrupts disabled. Does
> > 'gettimeofday' continue to run even when interrupts are disabled? If
> > not, is there anyway to count the RTC in systemtap?
>
> Calling gettimeofday is only a problem for probes in code sections that
> hold a write lock on xtime_lock. See bug #2525 for more details:
> http://sources.redhat.com/bugzilla/show_bug.cgi?id=2525
>
what if its an smp machine, and and someone else is calling
gettimeofday? seems like a race to me..
James Dickens
uadmin.blogspot.com
>
> Josh
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* RE: gettimeofday with interrupts disabled
@ 2006-05-08 22:29 Stone, Joshua I
0 siblings, 0 replies; 5+ messages in thread
From: Stone, Joshua I @ 2006-05-08 22:29 UTC (permalink / raw)
To: James Dickens; +Cc: azizeker, systemtap
On Monday, May 08, 2006 3:12 PM, James Dickens wrote:
> On 5/8/06, Stone, Joshua I <joshua.i.stone@intel.com> wrote:
>> On Sunday, May 07, 2006 6:24 PM, Aziz Eker wrote:
>>> I want to get some measurements about the time scheduler_tick()
>>> function takes. To do that, I am finding time difference between the
>>> start and end of the function using 'gettimeofday_us'. However, the
>>> scheduler_tick() function is called with interrupts disabled. Does
>>> 'gettimeofday' continue to run even when interrupts are disabled? If
>>> not, is there anyway to count the RTC in systemtap?
>>
>> Calling gettimeofday is only a problem for probes in code sections
>> that hold a write lock on xtime_lock. See bug #2525 for more
>> details: http://sources.redhat.com/bugzilla/show_bug.cgi?id=2525
>>
> what if its an smp machine, and and someone else is calling
> gettimeofday? seems like a race to me..
A race for what? 'do_gettimeofday' only takes a read lock on
xtime_lock, and multiple read locks are perfectly fine.
Even if the read locks were exclusive, it still would not be a deadlock.
One thread would be left waiting for the other to release, but since
your scenario is running on independent CPUs, the lock will eventually
be released.
Josh
^ permalink raw reply [flat|nested] 5+ messages in thread
[parent not found: <2107e7ae0605071820v5e1c0819n6d59746963fa0114@mail.gmail.com>]
end of thread, other threads:[~2006-05-08 22:29 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2006-05-08 17:28 gettimeofday with interrupts disabled Stone, Joshua I
2006-05-08 22:12 ` James Dickens
-- strict thread matches above, loose matches on Subject: below --
2006-05-08 22:29 Stone, Joshua I
[not found] <2107e7ae0605071820v5e1c0819n6d59746963fa0114@mail.gmail.com>
2006-05-08 1:24 ` Aziz Eker
2006-05-08 2:24 ` Roland McGrath
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).