linux-kernel - [PATCH 1/2] perf bench futex: Use a 64-bit time

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Message-Id: <20211014055527.1238645-1-alistair.francis@opensource.wdc.com>
Date:   Thu, 14 Oct 2021 15:55:26 +1000
From:   Alistair Francis <alistair.francis@...nsource.wdc.com>
To:     linux-riscv@...ts.infradead.org, linux-perf-users@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, alistair23@...il.com,
        namhyung@...nel.org, jolsa@...hat.com,
        alexander.shishkin@...ux.intel.com, mark.rutland@....com,
        acme@...nel.org, dave@...olabs.net, dvhart@...radead.org,
        peterz@...radead.org, mingo@...hat.com, tglx@...utronix.de,
        atish.patra@....com, arnd@...db.de,
        Alistair Francis <alistair.francis@....com>
Subject: [PATCH 1/2] perf bench futex: Use a 64-bit time_t

From: Alistair Francis <alistair.francis@....com>

Convert tools/perf to only use a 64-bit time_t. On 64-bit architectures
this isn't a functional change. On 32-bit architectures we now only
perform 64-bit time_t syscalls (__NR_futex_time64) and use a struct
timespec64.

This won't work on kernels before 5.1, but as perf is tied to the kernel
that's ok.

This allows us to build perf for 32-bit architectures with 64-bit time_t
like RISC-V 32-bit.

Signed-off-by: Alistair Francis <alistair.francis@....com>
---
 tools/perf/bench/futex.h | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/tools/perf/bench/futex.h b/tools/perf/bench/futex.h
index b3853aac3021c..c1ca75657c32e 100644
--- a/tools/perf/bench/futex.h
+++ b/tools/perf/bench/futex.h
@@ -27,12 +27,17 @@ struct bench_futex_parameters {
 	unsigned int nrequeue;
 };
 
+struct timespec64 {
+	long long tv_sec;       /* seconds */
+	long long tv_nsec;      /* nanoseconds */
+};
+
 /**
  * futex() - SYS_futex syscall wrapper
  * @uaddr:	address of first futex
  * @op:		futex op code
  * @val:	typically expected value of uaddr, but varies by op
- * @timeout:	typically an absolute struct timespec (except where noted
+ * @timeout:	typically an absolute struct timespec64 (except where noted
  *		otherwise). Overloaded by some ops
  * @uaddr2:	address of second futex for some ops
  * @val3:	varies by op
@@ -47,15 +52,26 @@ struct bench_futex_parameters {
  * These argument descriptions are the defaults for all
  * like-named arguments in the following wrappers except where noted below.
  */
-#define futex(uaddr, op, val, timeout, uaddr2, val3, opflags) \
-	syscall(SYS_futex, uaddr, op | opflags, val, timeout, uaddr2, val3)
+/**
+ * We only support 64-bit time_t for the timeout.
+ * On 64-bit architectures we can use __NR_futex
+ * On 32-bit architectures we use __NR_futex_time64. This only works on kernel
+ * versions 5.1+.
+ */
+#if __BITS_PER_LONG == 64 || defined(__i386__)
+# define futex(uaddr, op, val, timeout, uaddr2, val3, opflags) \
+	syscall(__NR_futex, uaddr, op | opflags, val, timeout, uaddr2, val3)
+#else
+# define futex(uaddr, op, val, timeout, uaddr2, val3, opflags) \
+	syscall(__NR_futex_time64, uaddr, op | opflags, val, timeout, uaddr2, val3)
+#endif
 
 /**
  * futex_wait() - block on uaddr with optional timeout
  * @timeout:	relative timeout
  */
 static inline int
-futex_wait(u_int32_t *uaddr, u_int32_t val, struct timespec *timeout, int opflags)
+futex_wait(u_int32_t *uaddr, u_int32_t val, struct timespec64 *timeout, int opflags)
 {
 	return futex(uaddr, FUTEX_WAIT, val, timeout, NULL, 0, opflags);
 }
@@ -74,7 +90,7 @@ futex_wake(u_int32_t *uaddr, int nr_wake, int opflags)
  * futex_lock_pi() - block on uaddr as a PI mutex
  */
 static inline int
-futex_lock_pi(u_int32_t *uaddr, struct timespec *timeout, int opflags)
+futex_lock_pi(u_int32_t *uaddr, struct timespec64 *timeout, int opflags)
 {
 	return futex(uaddr, FUTEX_LOCK_PI, 0, timeout, NULL, 0, opflags);
 }
@@ -111,7 +127,7 @@ futex_cmp_requeue(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2, int nr_wak
  */
 static inline int
 futex_wait_requeue_pi(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2,
-		      struct timespec *timeout, int opflags)
+		      struct timespec64 *timeout, int opflags)
 {
 	return futex(uaddr, FUTEX_WAIT_REQUEUE_PI, val, timeout, uaddr2, 0,
 		     opflags);
-- 
2.31.1