[PATCH] s390/preempt: Enable PREEMPT_COUNT_64BIT
From: Heiko Carstens
Date: Sat May 09 2026 - 13:23:08 EST
Convert s390's preempt_count to 64 bit, and change
the preempt primitives accordingly.
Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
---
arch/s390/Kconfig | 1 +
arch/s390/include/asm/lowcore.h | 13 +++++++----
arch/s390/include/asm/preempt.h | 41 +++++++++++++++------------------
3 files changed, 29 insertions(+), 26 deletions(-)
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index ecbcbb781e40..efa52667b5d4 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -276,6 +276,7 @@ config S390
select PCI_MSI if PCI
select PCI_MSI_ARCH_FALLBACKS if PCI_MSI
select PCI_QUIRKS if PCI
+ select PREEMPT_COUNT_64BIT
select SPARSE_IRQ
select SWIOTLB
select SYSCTL_EXCEPTION_TRACE
diff --git a/arch/s390/include/asm/lowcore.h b/arch/s390/include/asm/lowcore.h
index 50ffe75adeb4..0974ab278169 100644
--- a/arch/s390/include/asm/lowcore.h
+++ b/arch/s390/include/asm/lowcore.h
@@ -160,10 +160,15 @@ struct lowcore {
/* SMP info area */
__u32 cpu_nr; /* 0x03a0 */
__u32 softirq_pending; /* 0x03a4 */
- __s32 preempt_count; /* 0x03a8 */
- __u32 spinlock_lockval; /* 0x03ac */
- __u32 spinlock_index; /* 0x03b0 */
- __u8 pad_0x03b4[0x03b8-0x03b4]; /* 0x03b4 */
+ union {
+ struct {
+ __u32 need_resched; /* 0x03a8 */
+ __u32 count; /* 0x03ac */
+ } preempt;
+ __u64 preempt_count; /* 0x03a8 */
+ };
+ __u32 spinlock_lockval; /* 0x03b0 */
+ __u32 spinlock_index; /* 0x03b4 */
__u64 percpu_offset; /* 0x03b8 */
__u8 pad_0x03c0[0x0400-0x03c0]; /* 0x03c0 */
diff --git a/arch/s390/include/asm/preempt.h b/arch/s390/include/asm/preempt.h
index 0a25d4648b4c..1d5e4d7e9e1b 100644
--- a/arch/s390/include/asm/preempt.h
+++ b/arch/s390/include/asm/preempt.h
@@ -8,11 +8,8 @@
#include <asm/cmpxchg.h>
#include <asm/march.h>
-/*
- * Use MSB so it is possible to read preempt_count with LLGT which
- * reads the least significant 31 bits with a single instruction.
- */
-#define PREEMPT_NEED_RESCHED 0x80000000
+/* Use MSB for PREEMPT_NEED_RESCHED mostly because it is available. */
+#define PREEMPT_NEED_RESCHED 0x8000000000000000UL
/*
* We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
@@ -26,25 +23,25 @@
*/
static __always_inline int preempt_count(void)
{
- unsigned long lc_preempt, count;
+ unsigned long lc_preempt;
+ int count;
- BUILD_BUG_ON(sizeof_field(struct lowcore, preempt_count) != sizeof(int));
- lc_preempt = offsetof(struct lowcore, preempt_count);
+ lc_preempt = offsetof(struct lowcore, preempt.count);
/* READ_ONCE(get_lowcore()->preempt_count) & ~PREEMPT_NEED_RESCHED */
asm_inline(
- ALTERNATIVE("llgt %[count],%[offzero](%%r0)\n",
- "llgt %[count],%[offalt](%%r0)\n",
+ ALTERNATIVE("ly %[count],%[offzero](%%r0)\n",
+ "ly %[count],%[offalt](%%r0)\n",
ALT_FEATURE(MFEATURE_LOWCORE))
: [count] "=d" (count)
: [offzero] "i" (lc_preempt),
[offalt] "i" (lc_preempt + LOWCORE_ALT_ADDRESS),
- "m" (((struct lowcore *)0)->preempt_count));
+ "m" (((struct lowcore *)0)->preempt.count));
return count;
}
-static __always_inline void preempt_count_set(int pc)
+static __always_inline void preempt_count_set(unsigned long pc)
{
- int old, new;
+ unsigned long old, new;
old = READ_ONCE(get_lowcore()->preempt_count);
do {
@@ -63,12 +60,12 @@ static __always_inline void preempt_count_set(int pc)
static __always_inline void set_preempt_need_resched(void)
{
- __atomic_and(~PREEMPT_NEED_RESCHED, &get_lowcore()->preempt_count);
+ __atomic64_and(~PREEMPT_NEED_RESCHED, (long *)&get_lowcore()->preempt_count);
}
static __always_inline void clear_preempt_need_resched(void)
{
- __atomic_or(PREEMPT_NEED_RESCHED, &get_lowcore()->preempt_count);
+ __atomic64_or(PREEMPT_NEED_RESCHED, (long *)&get_lowcore()->preempt_count);
}
static __always_inline bool test_preempt_need_resched(void)
@@ -88,8 +85,8 @@ static __always_inline void __preempt_count_add(int val)
lc_preempt = offsetof(struct lowcore, preempt_count);
asm_inline(
- ALTERNATIVE("asi %[offzero](%%r0),%[val]\n",
- "asi %[offalt](%%r0),%[val]\n",
+ ALTERNATIVE("agsi %[offzero](%%r0),%[val]\n",
+ "agsi %[offalt](%%r0),%[val]\n",
ALT_FEATURE(MFEATURE_LOWCORE))
: "+m" (((struct lowcore *)0)->preempt_count)
: [offzero] "i" (lc_preempt), [val] "i" (val),
@@ -98,7 +95,7 @@ static __always_inline void __preempt_count_add(int val)
return;
}
}
- __atomic_add(val, &get_lowcore()->preempt_count);
+ __atomic64_add(val, (long *)&get_lowcore()->preempt_count);
}
static __always_inline void __preempt_count_sub(int val)
@@ -119,15 +116,15 @@ static __always_inline bool __preempt_count_dec_and_test(void)
lc_preempt = offsetof(struct lowcore, preempt_count);
asm_inline(
- ALTERNATIVE("alsi %[offzero](%%r0),%[val]\n",
- "alsi %[offalt](%%r0),%[val]\n",
+ ALTERNATIVE("algsi %[offzero](%%r0),%[val]\n",
+ "algsi %[offalt](%%r0),%[val]\n",
ALT_FEATURE(MFEATURE_LOWCORE))
: "=@cc" (cc), "+m" (((struct lowcore *)0)->preempt_count)
: [offzero] "i" (lc_preempt), [val] "i" (-1),
[offalt] "i" (lc_preempt + LOWCORE_ALT_ADDRESS));
return (cc == 0) || (cc == 2);
#else
- return __atomic_add_const_and_test(-1, &get_lowcore()->preempt_count);
+ return __atomic64_add_const_and_test(-1, (long *)&get_lowcore()->preempt_count);
#endif
}
@@ -141,7 +138,7 @@ static __always_inline bool should_resched(int preempt_offset)
static __always_inline int __preempt_count_add_return(int val)
{
- return val + __atomic_add(val, &get_lowcore()->preempt_count);
+ return val + __atomic64_add(val, (long *)&get_lowcore()->preempt_count);
}
static __always_inline int __preempt_count_sub_return(int val)
--
2.51.0