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Groups > linux.kernel > #1564532
| From | Frederic Weisbecker <fweisbec@gmail.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH 37/37] s390: Prevent from cputime leaks |
| Date | 2017-01-22 19:30 +0100 |
| Message-ID | <t2v3R-4ap-53@gated-at.bofh.it> (permalink) |
| References | <t2v3P-4ap-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
The s390 clock has a higher granularity than nanoseconds. 1 nanosec
equals 4.096 in s390 cputime_t. Therefore we leak a remainder while
flushing the cputime through cputime_to_nsecs().
For more precision, make sure we keep that remainder on cputime
accumulators for later accounting.
Reported-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
arch/s390/include/asm/cputime.h | 4 ++++
arch/s390/kernel/vtime.c | 33 +++++++++++++++++++++------------
2 files changed, 25 insertions(+), 12 deletions(-)
diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h
index d1c407d..86b5e3f 100644
--- a/arch/s390/include/asm/cputime.h
+++ b/arch/s390/include/asm/cputime.h
@@ -33,6 +33,10 @@ static inline unsigned int cputime_to_usecs(const cputime_t cputime)
return (__force unsigned long long) cputime >> 12;
}
+static inline cputime_t nsecs_to_cputime(u64 cputime)
+{
+ return (__force cputime_t) cputime * CPUTIME_PER_USEC * NSEC_PER_USEC;
+}
u64 arch_cpu_idle_time(int cpu);
diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index b4a3e9e..922f959 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -94,8 +94,14 @@ static inline u64 update_tsk_timer(unsigned long *tsk_vtime, u64 new)
{
u64 delta;
- delta = new - *tsk_vtime;
- *tsk_vtime = new;
+ /*
+ * Since nsecs is less granular than cputime_t in s390,
+ * the conversion to nsecs is rounded. Make sure we don't
+ * lose the remainder.
+ */
+ delta = cputime_to_nsecs(new - *tsk_vtime);
+ *tsk_vtime += nsecs_to_cputime(delta);
+
return delta;
}
@@ -124,7 +130,8 @@ static void account_system_index_scaled(struct task_struct *p,
*/
static int do_account_vtime(struct task_struct *tsk)
{
- u64 timer, clock, user, guest, system, hardirq, softirq, steal;
+ u64 timer, clock, delta;
+ u64 user, guest, system, hardirq, softirq, steal;
timer = S390_lowcore.last_update_timer;
clock = S390_lowcore.last_update_clock;
@@ -161,18 +168,19 @@ static int do_account_vtime(struct task_struct *tsk)
READ_ONCE(S390_lowcore.hardirq_timer));
softirq = update_tsk_timer(&tsk->thread.softirq_timer,
READ_ONCE(S390_lowcore.softirq_timer));
- S390_lowcore.steal_timer +=
- clock - user - guest - system - hardirq - softirq;
+
+ delta = nsecs_to_cputime(user + guest + system + hardirq + softirq);
+ S390_lowcore.steal_timer += clock - delta;
/* Push account value */
if (user) {
- account_user_time(tsk, cputime_to_nsecs(user));
- tsk->utimescaled += cputime_to_nsecs(scale_vtime(user));
+ account_user_time(tsk, user);
+ tsk->utimescaled += scale_vtime(user);
}
if (guest) {
- account_guest_time(tsk, cputime_to_nsecs(guest));
- tsk->utimescaled += cputime_to_nsecs(scale_vtime(guest));
+ account_guest_time(tsk, guest);
+ tsk->utimescaled += scale_vtime(guest);
}
if (system)
@@ -187,11 +195,12 @@ static int do_account_vtime(struct task_struct *tsk)
steal = S390_lowcore.steal_timer;
if ((s64) steal > 0) {
- S390_lowcore.steal_timer = 0;
- account_steal_time(cputime_to_nsecs(steal));
+ u64 nsecs = cputime_to_nsecs(steal);
+ S390_lowcore.steal_timer -= nsecs_to_cputime(nsecs);
+ account_steal_time(nsecs);
}
- return virt_timer_forward(user + guest + system + hardirq + softirq);
+ return virt_timer_forward(delta);
}
void vtime_task_switch(struct task_struct *prev)
--
2.7.4
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[PATCH 00/37] cputime: Convert core use of cputime_t to nsecs v3 Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 12/37] binfmt: Convert obsolete cputime type to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 16/37] signal: Convert obsolete cputime type to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 26/37] cputime: Complete nsec conversion of tick based accounting Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 36/37] cputime: Remove asm generic headers Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 09/37] alpha: Convert obsolete cputime_t to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 30/37] ia64: Convert vtime to use nsec units directly Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 04/37] cputime: Convert kcpustat to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 08/37] cputime: Convert task/group cputime to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
Re: [PATCH 08/37] cputime: Convert task/group cputime to nsecs Stanislaw Gruszka <sgruszka@redhat.com> - 2017-01-28 13:20 +0100
Re: [PATCH 08/37] cputime: Convert task/group cputime to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-28 16:40 +0100
Re: [PATCH 08/37] cputime: Convert task/group cputime to nsecs Stanislaw Gruszka <sgruszka@redhat.com> - 2017-01-30 15:00 +0100
Re: [PATCH 08/37] cputime: Convert task/group cputime to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-30 16:40 +0100
[PATCH 33/37] powerpc: Remove unused cputime definitions Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 07/37] cputime: Special API to return old-typed cputime Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 28/37] cputime: Remove jiffies based cputime Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 03/37] sched: Remove unused INIT_CPUTIME macro Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 10/37] x86: Convert obsolete cputime type to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 20/37] itimer: Convert internal cputime_t units to nsec Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 13/37] acct: Convert obsolete cputime type to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 05/37] macintosh/rack-meter: Remove cputime_t internal use Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 24/37] cputime: Push time to account_idle_time() in nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 34/37] s390: Remove unused cputime definitions Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 01/37] jiffies: Reuse TICK_NSEC instead of NSEC_PER_JIFFY Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 29/37] ia64: Move nsecs based cputime headers to the last arch using it Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 37/37] s390: Prevent from cputime leaks Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
Re: [PATCH 37/37] s390: Prevent from cputime leaks Martin Schwidefsky <schwidefsky@de.ibm.com> - 2017-01-23 10:50 +0100
Re: [PATCH 37/37] s390: Prevent from cputime leaks Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-25 16:30 +0100
Re: [PATCH 37/37] s390: Prevent from cputime leaks Martin Schwidefsky <schwidefsky@de.ibm.com> - 2017-01-25 16:50 +0100
[PATCH 27/37] vtime: Return nsecs instead of cputime_t to account Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 32/37] s390: Make arch_cpu_idle_time() to return nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 31/37] ia64: Remove unused cputime definitions Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 18/37] posix-timers: Use TICK_NSEC instead of a dynamically ad-hoc calculated version Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 02/37] time: Introduce jiffies64_to_nsecs() Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 15/37] tsacct: Convert obsolete cputime type to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 14/37] delaycct: Convert obsolete cputime type to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 25/37] cputime: Push time to account_system_time() in nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 23/37] cputime: Push time to account_steal_time() in nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 35/37] cputime: Remove unused nsec_to_cputime Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 19/37] posix-timers: Convert internals to use nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 17/37] cputime: Increment kcpustat directly on irqtime account Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
[PATCH 06/37] cputime: Convert guest time accounting to nsecs Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-22 19:30 +0100
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