Author: nyan
Date: Fri Nov 23 15:44:04 2012
New Revision: 243461
URL: http://svnweb.freebsd.org/changeset/base/243461
Log:
MFC: r225977, r242867, r242868, r242869
MFi386: r225936
Add some improvements in the idle table callbacks:
- Replace instances of manual assembly instruction "hlt" call
with halt() function calling.
- In cpu_idle_mwait() avoid races in check to sched_runnable() using
the same pattern used in cpu_idle_hlt() with the 'hlt' instruction.
- Add comments explaining the logic behind the pattern used in
cpu_idle_hlt() and other idle callbacks.
MFi386: r211924
Register an interrupt vector for DTrace return probes.
Fix some KASSERTs.
They are missing changes from r208833, r227394 and r227442.
Reduce diffs against i386.
Modified:
stable/8/sys/pc98/pc98/machdep.c
Directory Properties:
stable/8/sys/ (props changed)
stable/8/sys/pc98/ (props changed)
Modified: stable/8/sys/pc98/pc98/machdep.c
==============================================================================
--- stable/8/sys/pc98/pc98/machdep.c Fri Nov 23 15:42:25 2012
(r243460)
+++ stable/8/sys/pc98/pc98/machdep.c Fri Nov 23 15:44:04 2012
(r243461)
@@ -51,6 +51,7 @@ __FBSDID("$FreeBSD$");
#include "opt_maxmem.h"
#include "opt_npx.h"
#include "opt_perfmon.h"
+#include "opt_kdtrace.h"
#include <sys/param.h>
#include <sys/proc.h>
@@ -1122,7 +1123,7 @@ void
cpu_halt(void)
{
for (;;)
- __asm__ ("hlt");
+ halt();
}
static int idle_mwait = 1; /* Use MONITOR/MWAIT for short idle. */
@@ -1141,9 +1142,22 @@ cpu_idle_hlt(int busy)
state = (int *)PCPU_PTR(monitorbuf);
*state = STATE_SLEEPING;
+
/*
- * We must absolutely guarentee that hlt is the next instruction
- * after sti or we introduce a timing window.
+ * Since we may be in a critical section from cpu_idle(), if
+ * an interrupt fires during that critical section we may have
+ * a pending preemption. If the CPU halts, then that thread
+ * may not execute until a later interrupt awakens the CPU.
+ * To handle this race, check for a runnable thread after
+ * disabling interrupts and immediately return if one is
+ * found. Also, we must absolutely guarentee that hlt is
+ * the next instruction after sti. This ensures that any
+ * interrupt that fires after the call to disable_intr() will
+ * immediately awaken the CPU from hlt. Finally, please note
+ * that on x86 this works fine because of interrupts enabled only
+ * after the instruction following sti takes place, while IF is set
+ * to 1 immediately, allowing hlt instruction to acknowledge the
+ * interrupt.
*/
disable_intr();
if (sched_runnable())
@@ -1169,11 +1183,19 @@ cpu_idle_mwait(int busy)
state = (int *)PCPU_PTR(monitorbuf);
*state = STATE_MWAIT;
- if (!sched_runnable()) {
- cpu_monitor(state, 0, 0);
- if (*state == STATE_MWAIT)
- cpu_mwait(0, MWAIT_C1);
+
+ /* See comments in cpu_idle_hlt(). */
+ disable_intr();
+ if (sched_runnable()) {
+ enable_intr();
+ *state = STATE_RUNNING;
+ return;
}
+ cpu_monitor(state, 0, 0);
+ if (*state == STATE_MWAIT)
+ __asm __volatile("sti; mwait" : : "a" (MWAIT_C1), "c" (0));
+ else
+ enable_intr();
*state = STATE_RUNNING;
}
@@ -1185,6 +1207,12 @@ cpu_idle_spin(int busy)
state = (int *)PCPU_PTR(monitorbuf);
*state = STATE_RUNNING;
+
+ /*
+ * The sched_runnable() call is racy but as long as there is
+ * a loop missing it one time will have just a little impact if any
+ * (and it is much better than missing the check at all).
+ */
for (i = 0; i < 1000; i++) {
if (sched_runnable())
return;
@@ -1198,7 +1226,7 @@ void
cpu_idle(int busy)
{
-#ifdef SMP
+#if defined(SMP)
if (mp_grab_cpu_hlt())
return;
#endif
@@ -1708,7 +1736,11 @@ extern inthand_t
IDTVEC(bnd), IDTVEC(ill), IDTVEC(dna), IDTVEC(fpusegm),
IDTVEC(tss), IDTVEC(missing), IDTVEC(stk), IDTVEC(prot),
IDTVEC(page), IDTVEC(mchk), IDTVEC(rsvd), IDTVEC(fpu), IDTVEC(align),
- IDTVEC(xmm), IDTVEC(lcall_syscall), IDTVEC(int0x80_syscall);
+ IDTVEC(xmm),
+#ifdef KDTRACE_HOOKS
+ IDTVEC(dtrace_ret),
+#endif
+ IDTVEC(lcall_syscall), IDTVEC(int0x80_syscall);
#ifdef DDB
/*
@@ -2088,6 +2120,8 @@ do_next:
for (off = 0; off < round_page(msgbufsize); off += PAGE_SIZE)
pmap_kenter((vm_offset_t)msgbufp + off, phys_avail[pa_indx] +
off);
+
+ PT_UPDATES_FLUSH();
}
void
@@ -2227,6 +2261,10 @@ init386(first)
GSEL(GCODE_SEL, SEL_KPL));
setidt(IDT_SYSCALL, &IDTVEC(int0x80_syscall), SDT_SYS386TGT, SEL_UPL,
GSEL(GCODE_SEL, SEL_KPL));
+#ifdef KDTRACE_HOOKS
+ setidt(IDT_DTRACE_RET, &IDTVEC(dtrace_ret), SDT_SYS386TGT, SEL_UPL,
+ GSEL(GCODE_SEL, SEL_KPL));
+#endif
r_idt.rd_limit = sizeof(idt0) - 1;
r_idt.rd_base = (int) idt;
@@ -2563,7 +2601,8 @@ int
fill_fpregs(struct thread *td, struct fpreg *fpregs)
{
- KASSERT(td == curthread || TD_IS_SUSPENDED(td),
+ KASSERT(td == curthread || TD_IS_SUSPENDED(td) ||
+ P_SHOULDSTOP(td->td_proc),
("not suspended thread %p", td));
#ifdef DEV_NPX
npxgetregs(td);
@@ -2732,6 +2771,7 @@ static void
fpstate_drop(struct thread *td)
{
+ KASSERT(PCB_USER_FPU(td->td_pcb), ("fpstate_drop: kernel-owned fpu"));
critical_enter();
#ifdef DEV_NPX
if (PCPU_GET(fpcurthread) == td)
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