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Message-ID: <20240805184012.358023-2-ubizjak@gmail.com>
Date: Mon, 5 Aug 2024 20:38:59 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
Dennis Zhou <dennis@...nel.org>,
Tejun Heo <tj@...nel.org>,
Christoph Lameter <cl@...ux.com>,
Andy Lutomirski <luto@...nel.org>,
Ingo Molnar <mingo@...nel.org>,
Nadav Amit <nadav.amit@...il.com>,
Brian Gerst <brgerst@...il.com>,
Denys Vlasenko <dvlasenk@...hat.com>,
"H . Peter Anvin" <hpa@...or.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>,
Luc Van Oostenryck <luc.vanoostenryck@...il.com>
Subject: [RFC PATCH 1/3] percpu: Define __pcpu_typeof()
Define __pcpu_typeof() to use __typeof_unqual__() as typeof operator
when available, to return unqualified type of the expression.
If an arch defines __percpu variables in their own named address
space, then __pcpu_typeof() returns unqualified type of the
expression without named address space quialifier when
CONFIG_CC_HAS_TYPEOF_UNQUAL is defined.
Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Cc: Dennis Zhou <dennis@...nel.org>
Cc: Tejun Heo <tj@...nel.org>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Nadav Amit <nadav.amit@...il.com>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Luc Van Oostenryck <luc.vanoostenryck@...il.com>
---
arch/x86/include/asm/percpu.h | 38 ++++++++++++++++++++++------------
include/linux/part_stat.h | 2 +-
include/linux/percpu-defs.h | 39 ++++++++++++++++++++++++++++-------
init/Kconfig | 3 +++
kernel/locking/percpu-rwsem.c | 2 +-
5 files changed, 62 insertions(+), 22 deletions(-)
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index c55a79d5feae..4d31203eb0d2 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -73,10 +73,14 @@
unsigned long tcp_ptr__ = raw_cpu_read_long(this_cpu_off); \
\
tcp_ptr__ += (__force unsigned long)(_ptr); \
- (typeof(*(_ptr)) __kernel __force *)tcp_ptr__; \
+ (__pcpu_typeof(*(_ptr)) __kernel __force *)tcp_ptr__; \
})
#else
-#define arch_raw_cpu_ptr(_ptr) ({ BUILD_BUG(); (typeof(_ptr))0; })
+#define arch_raw_cpu_ptr(_ptr) \
+({ \
+ BUILD_BUG(); \
+ (__pcpu_typeof(*(_ptr)) __kernel __force *)0; \
+})
#endif
#define PER_CPU_VAR(var) %__percpu_seg:(var)__percpu_rel
@@ -172,7 +176,7 @@ do { \
: [val] __pcpu_reg_##size("=", pfo_val__) \
: [var] "m" (__my_cpu_var(_var))); \
\
- (typeof(_var))(unsigned long) pfo_val__; \
+ (__pcpu_typeof(_var))(unsigned long) pfo_val__; \
})
#define __raw_cpu_write(size, qual, _var, _val) \
@@ -180,7 +184,7 @@ do { \
__pcpu_type_##size pto_val__ = __pcpu_cast_##size(_val); \
\
if (0) { \
- typeof(_var) pto_tmp__; \
+ __pcpu_typeof(_var) pto_tmp__; \
pto_tmp__ = (_val); \
(void)pto_tmp__; \
} \
@@ -193,7 +197,11 @@ do { \
* The generic per-CPU infrastrucutre is not suitable for
* reading const-qualified variables.
*/
-#define __raw_cpu_read_const(pcp) ({ BUILD_BUG(); (typeof(pcp))0; })
+#define __raw_cpu_read_const(pcp) \
+({ \
+ BUILD_BUG(); \
+ (__pcpu_typeof(pcp))0; \
+})
#endif /* CONFIG_USE_X86_SEG_SUPPORT */
@@ -205,7 +213,7 @@ do { \
: [val] __pcpu_reg_##size("=", pfo_val__) \
: [var] "i" (&(_var))); \
\
- (typeof(_var))(unsigned long) pfo_val__; \
+ (__pcpu_typeof(_var))(unsigned long) pfo_val__; \
})
#define percpu_unary_op(size, qual, op, _var) \
@@ -219,7 +227,7 @@ do { \
__pcpu_type_##size pto_val__ = __pcpu_cast_##size(_val); \
\
if (0) { \
- typeof(_var) pto_tmp__; \
+ __pcpu_typeof(_var) pto_tmp__; \
pto_tmp__ = (_val); \
(void)pto_tmp__; \
} \
@@ -239,7 +247,7 @@ do { \
(int)(val) : 0; \
\
if (0) { \
- typeof(var) pao_tmp__; \
+ __pcpu_typeof(var) pao_tmp__; \
pao_tmp__ = (val); \
(void)pao_tmp__; \
} \
@@ -263,7 +271,7 @@ do { \
: [tmp] __pcpu_reg_##size("+", paro_tmp__), \
[var] "+m" (__my_cpu_var(_var)) \
: : "memory"); \
- (typeof(_var))(unsigned long) (paro_tmp__ + _val); \
+ (__pcpu_typeof(_var))(unsigned long) (paro_tmp__ + _val); \
})
/*
@@ -272,7 +280,7 @@ do { \
*/
#define raw_percpu_xchg_op(_var, _nval) \
({ \
- typeof(_var) pxo_old__ = raw_cpu_read(_var); \
+ __pcpu_typeof(_var) pxo_old__ = raw_cpu_read(_var); \
\
raw_cpu_write(_var, _nval); \
\
@@ -286,7 +294,7 @@ do { \
*/
#define this_percpu_xchg_op(_var, _nval) \
({ \
- typeof(_var) pxo_old__ = this_cpu_read(_var); \
+ __pcpu_typeof(_var) pxo_old__ = this_cpu_read(_var); \
\
do { } while (!this_cpu_try_cmpxchg(_var, &pxo_old__, _nval)); \
\
@@ -309,7 +317,7 @@ do { \
: [nval] __pcpu_reg_##size(, pco_new__) \
: "memory"); \
\
- (typeof(_var))(unsigned long) pco_old__; \
+ (__pcpu_typeof(_var))(unsigned long) pco_old__; \
})
#define percpu_try_cmpxchg_op(size, qual, _var, _ovalp, _nval) \
@@ -568,7 +576,11 @@ do { \
#else /* !CONFIG_X86_64: */
/* There is no generic 64-bit read stable operation for 32-bit targets. */
-#define this_cpu_read_stable_8(pcp) ({ BUILD_BUG(); (typeof(pcp))0; })
+#define this_cpu_read_stable_8(pcp) \
+({ \
+ BUILD_BUG(); \
+ (__pcpu_typeof(pcp))0; \
+})
#define raw_cpu_read_long(pcp) raw_cpu_read_4(pcp)
diff --git a/include/linux/part_stat.h b/include/linux/part_stat.h
index ac8c44dd8237..3807bc29ba05 100644
--- a/include/linux/part_stat.h
+++ b/include/linux/part_stat.h
@@ -33,7 +33,7 @@ struct disk_stats {
#define part_stat_read(part, field) \
({ \
- typeof((part)->bd_stats->field) res = 0; \
+ __pcpu_typeof((part)->bd_stats->field) res = 0; \
unsigned int _cpu; \
for_each_possible_cpu(_cpu) \
res += per_cpu_ptr((part)->bd_stats, _cpu)->field; \
diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
index 8efce7414fad..842d10912fdd 100644
--- a/include/linux/percpu-defs.h
+++ b/include/linux/percpu-defs.h
@@ -220,6 +220,21 @@ do { \
(void)__vpp_verify; \
} while (0)
+/*
+ * Define __percpu_typeof() to use __typeof_unqual__() as typeof
+ * operator when available, to return unqualified type of the exp.
+ *
+ * If an arch defines __percpu variables in their own named address
+ * space, then __pcpu_typeof() returns unqualified type of the
+ * expression without named address space qualifier when
+ * CONFIG_CC_HAS_TYPEOF_UNQUAL is defined.
+ */
+#ifdef CONFIG_CC_HAS_TYPEOF_UNQUAL
+#define __pcpu_typeof(exp) __typeof_unqual__(exp)
+#else
+#define __pcpu_typeof(exp) __typeof__(exp)
+#endif
+
#ifdef CONFIG_SMP
/*
@@ -228,7 +243,10 @@ do { \
* pointer value. The weird cast keeps both GCC and sparse happy.
*/
#define SHIFT_PERCPU_PTR(__p, __offset) \
- RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset))
+ uintptr_t ptr__ = (__force uintptr_t)(__p); \
+ \
+ RELOC_HIDE((__pcpu_typeof(*(__p)) __kernel __force *)(ptr__), \
+ (__offset))
#define per_cpu_ptr(ptr, cpu) \
({ \
@@ -254,13 +272,20 @@ do { \
#else /* CONFIG_SMP */
-#define VERIFY_PERCPU_PTR(__p) \
+#define PERCPU_PTR(__p) \
({ \
- __verify_pcpu_ptr(__p); \
- (typeof(*(__p)) __kernel __force *)(__p); \
+ uintptr_t ptr__ = (__force uintptr_t)(__p); \
+ \
+ (__pcpu_typeof(*(__p)) __kernel __force *)(ptr__); \
+})
+
+#define per_cpu_ptr(ptr, cpu) \
+({ \
+ __verify_pcpu_ptr(ptr); \
+ (void)(cpu); \
+ PERCPU_PTR(ptr); \
})
-#define per_cpu_ptr(ptr, cpu) ({ (void)(cpu); VERIFY_PERCPU_PTR(ptr); })
#define raw_cpu_ptr(ptr) per_cpu_ptr(ptr, 0)
#define this_cpu_ptr(ptr) raw_cpu_ptr(ptr)
@@ -315,7 +340,7 @@ static __always_inline void __this_cpu_preempt_check(const char *op) { }
#define __pcpu_size_call_return(stem, variable) \
({ \
- typeof(variable) pscr_ret__; \
+ __pcpu_typeof(variable) pscr_ret__; \
__verify_pcpu_ptr(&(variable)); \
switch(sizeof(variable)) { \
case 1: pscr_ret__ = stem##1(variable); break; \
@@ -330,7 +355,7 @@ static __always_inline void __this_cpu_preempt_check(const char *op) { }
#define __pcpu_size_call_return2(stem, variable, ...) \
({ \
- typeof(variable) pscr2_ret__; \
+ __pcpu_typeof(variable) pscr2_ret__; \
__verify_pcpu_ptr(&(variable)); \
switch(sizeof(variable)) { \
case 1: pscr2_ret__ = stem##1(variable, __VA_ARGS__); break; \
diff --git a/init/Kconfig b/init/Kconfig
index 37260d17267e..a9a04d0683b6 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -873,6 +873,9 @@ config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
config CC_HAS_INT128
def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
+config CC_HAS_TYPEOF_UNQUAL
+ def_bool $(success,echo 'int foo (int a) { __typeof_unqual__(a) b = a; return b; }' | $(CC) -x c - -S -o /dev/null)
+
config CC_IMPLICIT_FALLTHROUGH
string
default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index 6083883c4fe0..ac9b2f4bcd92 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -184,7 +184,7 @@ EXPORT_SYMBOL_GPL(__percpu_down_read);
#define per_cpu_sum(var) \
({ \
- typeof(var) __sum = 0; \
+ __pcpu_typeof(var) __sum = 0; \
int cpu; \
compiletime_assert_atomic_type(__sum); \
for_each_possible_cpu(cpu) \
--
2.45.2
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