Author: jhb
Date: Thu Nov 8 22:42:55 2018
New Revision: 340270
URL: https://svnweb.freebsd.org/changeset/base/340270
Log:
MFC 340164,340168,340170: Add custom cpu_lock_delay() for x86.
340164:
Add a KPI for the delay while spinning on a spin lock.
Replace a call to DELAY(1) with a new cpu_lock_delay() KPI. Currently
cpu_lock_delay() is defined to DELAY(1) on all platforms. However,
platforms with a DELAY() implementation that uses spin locks should
implement a custom cpu_lock_delay() doesn't use locks.
340168:
Add a delay_tsc() static function for when DELAY() uses the TSC.
This uses slightly simpler logic than the existing code by using the
full 64-bit counter and thus not having to worry about counter
overflow.
340170:
Add a custom implementation of cpu_lock_delay() for x86.
Avoid using DELAY() since it can try to use spin locks on CPUs without
a P-state invariant TSC. For cpu_lock_delay(), always use the TSC if
it exists (even if it is not P-state invariant) to delay for a
microsecond. If the TSC does not exist, read from I/O port 0x84 to
delay instead.
PR: 228768
Modified:
stable/11/sys/amd64/include/cpu.h
stable/11/sys/arm/include/cpu.h
stable/11/sys/arm64/include/cpu.h
stable/11/sys/i386/include/cpu.h
stable/11/sys/kern/kern_mutex.c
stable/11/sys/mips/include/cpu.h
stable/11/sys/powerpc/include/cpu.h
stable/11/sys/riscv/include/cpu.h
stable/11/sys/sparc64/include/cpu.h
stable/11/sys/x86/x86/delay.c
Directory Properties:
stable/11/ (props changed)
Modified: stable/11/sys/amd64/include/cpu.h
==============================================================================
--- stable/11/sys/amd64/include/cpu.h Thu Nov 8 22:39:38 2018
(r340269)
+++ stable/11/sys/amd64/include/cpu.h Thu Nov 8 22:42:55 2018
(r340270)
@@ -73,6 +73,7 @@ extern char etext[];
extern void (*vmm_resume_p)(void);
void cpu_halt(void);
+void cpu_lock_delay(void);
void cpu_reset(void);
void fork_trampoline(void);
void swi_vm(void *);
Modified: stable/11/sys/arm/include/cpu.h
==============================================================================
--- stable/11/sys/arm/include/cpu.h Thu Nov 8 22:39:38 2018
(r340269)
+++ stable/11/sys/arm/include/cpu.h Thu Nov 8 22:42:55 2018
(r340270)
@@ -61,6 +61,7 @@ get_cyclecount(void)
#define cpu_getstack(td) ((td)->td_frame->tf_usr_sp)
#define cpu_setstack(td, sp) ((td)->td_frame->tf_usr_sp = (sp))
#define cpu_spinwait() /* nothing */
+#define cpu_lock_delay() DELAY(1)
#define ARM_NVEC 8
#define ARM_VEC_ALL 0xffffffff
Modified: stable/11/sys/arm64/include/cpu.h
==============================================================================
--- stable/11/sys/arm64/include/cpu.h Thu Nov 8 22:39:38 2018
(r340269)
+++ stable/11/sys/arm64/include/cpu.h Thu Nov 8 22:42:55 2018
(r340270)
@@ -51,6 +51,7 @@
#define cpu_getstack(td) ((td)->td_frame->tf_sp)
#define cpu_setstack(td, sp) ((td)->td_frame->tf_sp = (sp))
#define cpu_spinwait() __asm __volatile("yield" ::: "memory")
+#define cpu_lock_delay() DELAY(1)
/* Extract CPU affinity levels 0-3 */
#define CPU_AFF0(mpidr) (u_int)(((mpidr) >> 0) & 0xff)
Modified: stable/11/sys/i386/include/cpu.h
==============================================================================
--- stable/11/sys/i386/include/cpu.h Thu Nov 8 22:39:38 2018
(r340269)
+++ stable/11/sys/i386/include/cpu.h Thu Nov 8 22:42:55 2018
(r340270)
@@ -70,6 +70,7 @@ extern char btext[];
extern char etext[];
void cpu_halt(void);
+void cpu_lock_delay(void);
void cpu_reset(void);
void fork_trampoline(void);
void swi_vm(void *);
Modified: stable/11/sys/kern/kern_mutex.c
==============================================================================
--- stable/11/sys/kern/kern_mutex.c Thu Nov 8 22:39:38 2018
(r340269)
+++ stable/11/sys/kern/kern_mutex.c Thu Nov 8 22:42:55 2018
(r340270)
@@ -1204,7 +1204,7 @@ _mtx_lock_indefinite_check(struct mtx *m, struct lock_
ldap->spin_cnt++;
if (ldap->spin_cnt < 60000000 || kdb_active || panicstr != NULL)
- DELAY(1);
+ cpu_lock_delay();
else {
td = mtx_owner(m);
Modified: stable/11/sys/mips/include/cpu.h
==============================================================================
--- stable/11/sys/mips/include/cpu.h Thu Nov 8 22:39:38 2018
(r340269)
+++ stable/11/sys/mips/include/cpu.h Thu Nov 8 22:42:55 2018
(r340270)
@@ -69,6 +69,7 @@
#define cpu_getstack(td) ((td)->td_frame->sp)
#define cpu_setstack(td, nsp) ((td)->td_frame->sp = (nsp))
#define cpu_spinwait() /* nothing */
+#define cpu_lock_delay() DELAY(1)
/*
* A machine-independent interface to the CPU's counter.
Modified: stable/11/sys/powerpc/include/cpu.h
==============================================================================
--- stable/11/sys/powerpc/include/cpu.h Thu Nov 8 22:39:38 2018
(r340269)
+++ stable/11/sys/powerpc/include/cpu.h Thu Nov 8 22:42:55 2018
(r340270)
@@ -101,6 +101,7 @@ get_cyclecount(void)
#define cpu_getstack(td) ((td)->td_frame->fixreg[1])
#define cpu_spinwait() __asm __volatile("or 27,27,27") /*
yield */
+#define cpu_lock_delay() DELAY(1)
extern char btext[];
extern char etext[];
Modified: stable/11/sys/riscv/include/cpu.h
==============================================================================
--- stable/11/sys/riscv/include/cpu.h Thu Nov 8 22:39:38 2018
(r340269)
+++ stable/11/sys/riscv/include/cpu.h Thu Nov 8 22:42:55 2018
(r340270)
@@ -46,6 +46,7 @@
#define cpu_getstack(td) ((td)->td_frame->tf_sp)
#define cpu_setstack(td, sp) ((td)->td_frame->tf_sp = (sp))
#define cpu_spinwait() /* nothing */
+#define cpu_lock_delay() DELAY(1)
#ifdef _KERNEL
Modified: stable/11/sys/sparc64/include/cpu.h
==============================================================================
--- stable/11/sys/sparc64/include/cpu.h Thu Nov 8 22:39:38 2018
(r340269)
+++ stable/11/sys/sparc64/include/cpu.h Thu Nov 8 22:42:55 2018
(r340270)
@@ -46,6 +46,7 @@
#define cpu_getstack(td) ((td)->td_frame->tf_sp)
#define cpu_setstack(td, sp) ((td)->td_frame->tf_sp = (sp))
#define cpu_spinwait() /* nothing */
+#define cpu_lock_delay() DELAY(1)
#ifdef _KERNEL
Modified: stable/11/sys/x86/x86/delay.c
==============================================================================
--- stable/11/sys/x86/x86/delay.c Thu Nov 8 22:39:38 2018
(r340269)
+++ stable/11/sys/x86/x86/delay.c Thu Nov 8 22:42:55 2018
(r340270)
@@ -49,11 +49,23 @@ __FBSDID("$FreeBSD$");
#include <machine/cpu.h>
#include <x86/init.h>
-static u_int
-get_tsc(__unused struct timecounter *tc)
+static void
+delay_tsc(int n)
{
+ uint64_t end, now;
- return (rdtsc32());
+ /*
+ * Pin the current thread ensure correct behavior if the TSCs
+ * on different CPUs are not in sync.
+ */
+ sched_pin();
+ now = rdtsc();
+ end = now + tsc_freq * n / 1000000;
+ do {
+ cpu_spinwait();
+ now = rdtsc();
+ } while (now < end);
+ sched_unpin();
}
static int
@@ -64,22 +76,24 @@ delay_tc(int n)
uint64_t end, freq, now;
u_int last, mask, u;
- tc = timecounter;
- freq = atomic_load_acq_64(&tsc_freq);
- if (tsc_is_invariant && freq != 0) {
- func = get_tsc;
- mask = ~0u;
- } else {
- if (tc->tc_quality <= 0)
- return (0);
- func = tc->tc_get_timecount;
- mask = tc->tc_counter_mask;
- freq = tc->tc_frequency;
+ /*
+ * Only use the TSC if it is P-state invariant. If the TSC is
+ * not P-state invariant and the CPU is not running at the
+ * "full" P-state, then the TSC will increment at some rate
+ * less than tsc_freq and delay_tsc() will wait too long.
+ */
+ if (tsc_is_invariant && tsc_freq != 0) {
+ delay_tsc(n);
+ return (1);
}
+ tc = timecounter;
+ if (tc->tc_quality <= 0)
+ return (0);
+ func = tc->tc_get_timecount;
+ mask = tc->tc_counter_mask;
+ freq = tc->tc_frequency;
now = 0;
end = freq * n / 1000000;
- if (func == get_tsc)
- sched_pin();
last = func(tc) & mask;
do {
cpu_spinwait();
@@ -90,8 +104,6 @@ delay_tc(int n)
now += u - last;
last = u;
} while (now < end);
- if (func == get_tsc)
- sched_unpin();
return (1);
}
@@ -103,4 +115,23 @@ DELAY(int n)
return;
init_ops.early_delay(n);
+}
+
+void
+cpu_lock_delay(void)
+{
+
+ /*
+ * Use TSC to wait for a usec if present, otherwise fall back
+ * to reading from port 0x84. We can't call into timecounters
+ * for this delay since timecounters might use spin locks.
+ *
+ * Note that unlike delay_tc(), this uses the TSC even if it
+ * is not P-state invariant. For this function it is ok to
+ * wait even a few usecs.
+ */
+ if (tsc_freq != 0)
+ delay_tsc(1);
+ else
+ inb(0x84);
}
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