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authorHeiko Carstens <heiko.carstens@de.ibm.com>2008-10-03 21:54:59 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2008-10-03 21:55:54 +0200
commitd3d238c7744d08c36a114a59cb537d4c0c6c9a86 (patch)
treedf5d69d40dbdaf5e5014a6ce41909e7236a196c1 /arch/s390/lib
parent95b866d5afcafee00fc9ad70665e48c86d8c4e0f (diff)
downloadlinux-linaro-android-d3d238c7744d08c36a114a59cb537d4c0c6c9a86.tar.gz
[S390] nohz: Fix __udelay.
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>
Diffstat (limited to 'arch/s390/lib')
-rw-r--r--arch/s390/lib/delay.c88
1 files changed, 54 insertions, 34 deletions
diff --git a/arch/s390/lib/delay.c b/arch/s390/lib/delay.c
index fc6ab6094df..0953cee05ef 100644
--- a/arch/s390/lib/delay.c
+++ b/arch/s390/lib/delay.c
@@ -1,14 +1,9 @@
/*
- * arch/s390/lib/delay.c
* Precise Delay Loops for S390
*
- * S390 version
- * Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
- * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
- *
- * Derived from "arch/i386/lib/delay.c"
- * Copyright (C) 1993 Linus Torvalds
- * Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
+ * Copyright IBM Corp. 1999,2008
+ * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
+ * Heiko Carstens <heiko.carstens@de.ibm.com>,
*/
#include <linux/sched.h>
@@ -29,30 +24,31 @@ void __delay(unsigned long loops)
asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
}
-/*
- * Waits for 'usecs' microseconds using the TOD clock comparator.
- */
-void __udelay(unsigned long usecs)
+static void __udelay_disabled(unsigned long usecs)
{
- u64 end, time, old_cc = 0;
- unsigned long flags, cr0, mask, dummy;
- int irq_context;
+ unsigned long mask, cr0, cr0_saved;
+ u64 clock_saved;
- irq_context = in_interrupt();
- if (!irq_context)
- local_bh_disable();
- local_irq_save(flags);
- if (raw_irqs_disabled_flags(flags)) {
- old_cc = local_tick_disable();
- S390_lowcore.clock_comparator = -1ULL;
- __ctl_store(cr0, 0, 0);
- dummy = (cr0 & 0xffff00e0) | 0x00000800;
- __ctl_load(dummy , 0, 0);
- mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
- } else
- mask = psw_kernel_bits | PSW_MASK_WAIT |
- PSW_MASK_EXT | PSW_MASK_IO;
+ clock_saved = local_tick_disable();
+ set_clock_comparator(get_clock() + ((u64) usecs << 12));
+ __ctl_store(cr0_saved, 0, 0);
+ cr0 = (cr0_saved & 0xffff00e0) | 0x00000800;
+ __ctl_load(cr0 , 0, 0);
+ mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
+ trace_hardirqs_on();
+ __load_psw_mask(mask);
+ local_irq_disable();
+ __ctl_load(cr0_saved, 0, 0);
+ local_tick_enable(clock_saved);
+ set_clock_comparator(S390_lowcore.clock_comparator);
+}
+static void __udelay_enabled(unsigned long usecs)
+{
+ unsigned long mask;
+ u64 end, time;
+
+ mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO;
end = get_clock() + ((u64) usecs << 12);
do {
time = end < S390_lowcore.clock_comparator ?
@@ -62,13 +58,37 @@ void __udelay(unsigned long usecs)
__load_psw_mask(mask);
local_irq_disable();
} while (get_clock() < end);
+ set_clock_comparator(S390_lowcore.clock_comparator);
+}
- if (raw_irqs_disabled_flags(flags)) {
- __ctl_load(cr0, 0, 0);
- local_tick_enable(old_cc);
+/*
+ * Waits for 'usecs' microseconds using the TOD clock comparator.
+ */
+void __udelay(unsigned long usecs)
+{
+ unsigned long flags;
+
+ preempt_disable();
+ local_irq_save(flags);
+ if (in_irq()) {
+ __udelay_disabled(usecs);
+ goto out;
+ }
+ if (in_softirq()) {
+ if (raw_irqs_disabled_flags(flags))
+ __udelay_disabled(usecs);
+ else
+ __udelay_enabled(usecs);
+ goto out;
}
- if (!irq_context)
+ if (raw_irqs_disabled_flags(flags)) {
+ local_bh_disable();
+ __udelay_disabled(usecs);
_local_bh_enable();
- set_clock_comparator(S390_lowcore.clock_comparator);
+ goto out;
+ }
+ __udelay_enabled(usecs);
+out:
local_irq_restore(flags);
+ preempt_enable();
}