linux/include
Venkatesh Pallipadi 75e1056f5c sched: Fix softirq time accounting
Peter Zijlstra found a bug in the way softirq time is accounted in
VIRT_CPU_ACCOUNTING on this thread:

   http://lkml.indiana.edu/hypermail//linux/kernel/1009.2/01366.html

The problem is, softirq processing uses local_bh_disable internally. There
is no way, later in the flow, to differentiate between whether softirq is
being processed or is it just that bh has been disabled. So, a hardirq when bh
is disabled results in time being wrongly accounted as softirq.

Looking at the code a bit more, the problem exists in !VIRT_CPU_ACCOUNTING
as well. As account_system_time() in normal tick based accouting also uses
softirq_count, which will be set even when not in softirq with bh disabled.

Peter also suggested solution of using 2*SOFTIRQ_OFFSET as irq count
for local_bh_{disable,enable} and using just SOFTIRQ_OFFSET while softirq
processing. The patch below does that and adds API in_serving_softirq() which
returns whether we are currently processing softirq or not.

Also changes one of the usages of softirq_count in net/sched/cls_cgroup.c
to in_serving_softirq.

Looks like many usages of in_softirq really want in_serving_softirq. Those
changes can be made individually on a case by case basis.

Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286237003-12406-2-git-send-email-venki@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18 20:52:20 +02:00
..
acpi ACPI: Fix typos 2010-09-28 21:38:19 -04:00
asm-generic gpio: doc updates 2010-09-09 18:57:24 -07:00
crypto
drm drm/ttm: Fix two race conditions + fix busy codepaths 2010-10-06 09:04:43 +10:00
keys DNS: Separate out CIFS DNS Resolver code 2010-08-05 17:17:51 +00:00
linux sched: Fix softirq time accounting 2010-10-18 20:52:20 +02:00
math-emu
media V4L/DVB: videobuf-dma-sg: set correct size in last sg element 2010-09-27 22:22:01 -03:00
mtd mtd: Update copyright notices 2010-08-08 20:58:20 +01:00
net Bluetooth: Fix deadlock in the ERTM logic 2010-09-30 12:19:35 -03:00
pcmcia pcmcia: use struct resource for PCMCIA devices, part 2 2010-08-03 09:04:16 +02:00
rdma IB: Rename RAW_ETY to RAW_ETHERTYPE 2010-08-04 10:44:19 -07:00
rxrpc
scsi scsi: use __uX types for headers exported to user space 2010-08-11 08:59:01 -07:00
sound ALSA: emu10k1 - delay the PCM interrupts (add pcm_irq_delay parameter) 2010-08-18 15:10:59 +02:00
trace tracing/sched: Add sched_pi_setprio tracepoint 2010-09-21 10:56:41 -04:00
video include: replace unifdef-y with header-y 2010-08-14 22:26:51 +02:00
xen xen: pvhvm: make it clearer that XEN_UNPLUG_* define bits in a bitfield 2010-08-23 12:01:35 +01:00
Kbuild