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Use an own implementation instead of the common code udelay loop.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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When udelay() gets called with a delay that would expire before the
next clock event it reprograms the clock comparator.
When the interrupt happens the clock comparator won't be resetted
therefore the interrupt condition doesn't get cleared.
The result is an endless timer interrupt loop until the next clock
event would expire (stored in lowcore).
So udelay() usually would wait much longer for small delays than it
should.
Fix this by disabling the local tick which makes sure that the clock
comparator will be resetted when a timer interrupt happens.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Our udelay implementation enables interrupts to receive a special timer
interrupt regardless of the context it is called from.
This might lead to false positive lockdep reports. Since lockdep isn't
aware of the fact that only a single interrupt source is enabled it
warns about possible deadlocks that in reality won't happen, like
the one below.
To fix this disable lockdep before enabling interrupts.
[ 254.040888] =================================
[ 254.040904] [ INFO: inconsistent lock state ]
[ 254.040910] 2.6.30 #9
[ 254.040914] ---------------------------------
[ 254.040920] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
[ 254.040927] swapper/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
[ 254.040934] (sch->lock){?.-...}, at: [<00000000002e4778>] ccw_device_timeout+0x48/0x2f0
[ 254.040961] {IN-HARDIRQ-W} state was registered at:
[ 254.040969] [<0000000000096f74>] __lock_acquire+0x9d4/0x188c
[ 254.040985] [<0000000000097f68>] lock_acquire+0x13c/0x16c
[ 254.040998] [<00000000004527e0>] _spin_lock+0x74/0xb8
[ 254.041016] [<0000000000457eb2>] do_IRQ+0xde/0x208
[ 254.041031] [<000000000002d190>] io_return+0x0/0x8
[ 254.041049] [<0000000000029faa>] vtime_stop_cpu+0xbe/0x114
[ 254.041066] irq event stamp: 259629
[ 254.041076] hardirqs last enabled at (259628): [<000000000045238e>] _spin_unlock_irq+0x5e/0x9c
[ 254.041095] hardirqs last disabled at (259629): [<000000000045292e>] _spin_lock_irq+0x4a/0xc4
[ 254.041126] softirqs last enabled at (259614): [<000000000006500e>] __do_softirq+0x296/0x2b0
[ 254.041137] softirqs last disabled at (259619): [<0000000000024cf6>] do_softirq+0x102/0x108
[ 254.041147]
[ 254.041148] other info that might help us debug this:
[ 254.041153] 2 locks held by swapper/0:
[ 254.041157] #0: (&priv->timer){+.-...}, at: [<000000000006bf9a>] run_timer_softirq+0x19a/0x340
[ 254.041170] #1: (sch->lock){?.-...}, at: [<00000000002e4778>] ccw_device_timeout+0x48/0x2f0
[ 254.041182]
[ 254.041310] Call Trace:
[ 254.041313] ([<00000000000174fc>] show_trace+0x16c/0x170)
[ 254.041321] [<0000000000017578>] show_stack+0x78/0x104
[ 254.041327] [<000000000044d0ca>] dump_stack+0xc6/0xd4
[ 254.041342] [<00000000000949b4>] print_usage_bug+0x1c8/0x1fc
[ 254.041353] [<0000000000094e8a>] mark_lock+0x4a2/0x670
[ 254.041364] [<00000000000950e2>] mark_held_locks+0x8a/0xb4
[ 254.041375] [<0000000000095398>] trace_hardirqs_on_caller+0x74/0x1ac
[ 254.041388] [<00000000000954fa>] trace_hardirqs_on+0x2a/0x38
[ 254.041402] [<000000000025f1ec>] __udelay_disabled+0xac/0xfc
[ 254.041419] [<000000000025f432>] __udelay+0x12a/0x148
[ 254.041433] [<00000000002d64d8>] cio_commit_config+0x170/0x290
[ 254.041451] [<00000000002d6978>] cio_disable_subchannel+0x120/0x1cc
[ 254.041468] [<00000000002e32a4>] ccw_device_recog_done+0x54/0x2f4
[ 254.041485] [<00000000002e3638>] ccw_device_sense_id_done+0x50/0x90
[ 254.041508] [<00000000002e615a>] snsid_callback+0xfa/0x3a8
[ 254.041515] [<00000000002dd96c>] ccwreq_stop+0x80/0x90
[ 254.041523] [<00000000002dda8e>] ccw_request_timeout+0xc2/0xd0
[ 254.041530] [<00000000002e2f70>] ccw_device_request_event+0x58/0x90
[ 254.041537] [<00000000002e47ae>] ccw_device_timeout+0x7e/0x2f0
[ 254.041555] [<000000000006c02a>] run_timer_softirq+0x22a/0x340
[ 254.041566] [<0000000000064eb0>] __do_softirq+0x138/0x2b0
[ 254.041578] [<0000000000024cf6>] do_softirq+0x102/0x108
[ 254.041590] [<00000000000647ce>] irq_exit+0xee/0x114
[ 254.041603] [<0000000000457d88>] do_extint+0x130/0x17c
[ 254.041617] [<000000000002d41e>] ext_no_vtime+0x1e/0x22
[ 254.041631] [<0000000000029faa>] vtime_stop_cpu+0xbe/0x114
[ 254.041646] ([<0000000000029f58>] vtime_stop_cpu+0x6c/0x114)
[ 254.041662] [<000000000001d842>] cpu_idle+0x122/0x1c0
[ 254.041679] [<00000000004482c6>] start_secondary+0xce/0xe0
[ 254.041696] [<0000000000000000>] 0x0
[ 254.041715] [<0000000000000000>] 0x0
[ 254.041745] INFO: lockdep is turned off.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Move all EXPORT_SYMBOLs to their corresponding definitions.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Move cio's private simple udelay function to lib/delay.c and turn it
into something much more readable. So we have all implementations
at one place.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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This fixes a regression that came with 934b2857cc576ae53c92a66e63fce7ddcfa74691
("[S390] nohz/sclp: disable timer on synchronous waits.").
If udelay() gets called from a disabled context it sets the clock comparator
to a value where it expects the next interrupt. When the interrupt happens
the clock comparator gets not reset and therefore the interrupt condition
doesn't get cleared. The result is an endless timer interrupt loop.
In addition this patch fixes also the following:
rcutorture reveals that our __udelay implementation is still buggy,
since it might schedule tasklets, but prevents their execution:
NOHZ: local_softirq_pending 42
NOHZ: local_softirq_pending 02
NOHZ: local_softirq_pending 142
NOHZ: local_softirq_pending 02
To fix this we make sure that only the clock comparator interrupt
is enabled when the enabled wait psw is loaded.
Also no code gets called anymore which might schedule tasklets.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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sclp_sync_wait wait synchronously for an sclp interrupt and disables
timer interrupts. However on the irq enter paths there is an extra
check if a timer interrupt would be due and calls the timer callback.
This would schedule softirqs in the wrong context.
So introduce local_tick_enable/disable which prevents this.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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This way we get rid of s390's NO_IDLE_HZ and use the generic dynticks
variant instead. In addition we get high resolution timers for free.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
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The new delay implementation uses the clock comparator and an external
interrupt even if it is called disabled for interrupts. To do this
all external interrupt source except clock comparator are switched of
before enabling external interrupts. The external interrupt at the
end of the delay period may not execute softirqs or we can end up in a
dead-lock.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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This patch adds support for clock synchronization to an external time
reference (ETR). The external time reference sends an oscillator
signal and a synchronization signal every 2^20 microseconds to keep
the TOD clocks of all connected servers in sync. For availability
two ETR units can be connected to a machine. If the clock deviates
for more than the sync-check tolerance all cpus get a machine check
that indicates that the clock is out of sync. For the lovely details
how to get the clock back in sync see the code below.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Major cleanup of all s390 inline assemblies. They now have a common
coding style. Quite a few have been shortened, mainly by using register
asm variables. Use of the EX_TABLE macro helps as well. The atomic ops,
bit ops and locking inlines new use the Q-constraint if a newer gcc
is used. That results in slightly better code.
Thanks to Christian Borntraeger for proof reading the changes.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Signed-off-by: Jörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
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Fix __delay implementation. Called with an argument "1" or "0" it would
loop nearly forever (since (1/2)-1 = 0xffffffff).
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
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