From: Serge Belyshev <belyshev@depni.sinp.msu.ru>
To: Ingo Molnar <mingo@elte.hu>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [RT] fix delay in do_vgettimeofday() in arch/x86_64/kernel/vsyscall.c
Date: Fri, 09 Dec 2005 22:38:53 +0300 [thread overview]
Message-ID: <87d5k6ukky.fsf@foo.vault.bofh.ru> (raw)
There are occasional very very long (30..60 sec) delays happening when calling
gettimeofday() vsyscall on x86_64 with 2.6.14-rt22 kernel.
These delays come from while() looping over invalid data that are
going to be discarded by seqlock.
arch/x86_64/kernel/vsyscall.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
Index: linux/arch/x86_64/kernel/vsyscall.c
===================================================================
--- linux.orig/arch/x86_64/kernel/vsyscall.c
+++ linux/arch/x86_64/kernel/vsyscall.c
@@ -111,14 +111,15 @@ static force_inline void do_vgettimeofda
/* add nsec offset to wall_time_tv */
*tv = __vsyscall_gtod_data.wall_time_tv;
- do_div(nsec_delta, NSEC_PER_USEC);
- tv->tv_usec += (unsigned long) nsec_delta;
-
- while (tv->tv_usec > USEC_PER_SEC) {
- tv->tv_sec += 1;
- tv->tv_usec -= USEC_PER_SEC;
- }
} while (read_seqretry(&__vsyscall_gtod_lock, seq));
+
+ do_div(nsec_delta, NSEC_PER_USEC);
+ tv->tv_usec += (unsigned long) nsec_delta;
+
+ while (tv->tv_usec > USEC_PER_SEC) {
+ tv->tv_sec += 1;
+ tv->tv_usec -= USEC_PER_SEC;
+ }
}
/*
next reply other threads:[~2005-12-09 19:39 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-09 19:38 Serge Belyshev [this message]
2005-12-10 2:33 ` [RT] fix delay in do_vgettimeofday() in arch/x86_64/kernel/vsyscall.c john stultz
2005-12-10 20:56 ` Fernando Lopez-Lezcano
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