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Protect access to the AT realtime clock with its own mutex.

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The mutex protecting access to the registered realtime clock should not be
overloaded to protect access to the atrtc hardware, which might not even be
the registered rtc. More importantly, the resettodr mutex needs to be
eliminated to remove locking/sleeping restrictions on clock drivers, and
that can't happen if MD code for amd64 depends on it. This change moves the
protection into what's really being protected: access to the atrtc date and
time registers.

This change also adds protection when the clock is accessed from
xentimer_settime(), which bypasses the resettodr locking.

Differential Revision:	https://reviews.freebsd.org/D11483
This commit is contained in:
Ian Lepore 2017-07-12 02:42:57 +00:00
parent 15a88f8158
commit b524a31593
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=320901
3 changed files with 22 additions and 6 deletions
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13
sys/amd64/amd64/efirt.c
View File

@ -46,6 +46,7 @@ __FBSDID("$FreeBSD$");
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/vmmeter.h>
#include <isa/rtc.h>
#include <machine/fpu.h>
#include <machine/efi.h>
#include <machine/metadata.h>
@ -445,7 +446,7 @@ efi_get_time_locked(struct efi_tm *tm)
efi_status status;
int error;
mtx_assert(&resettodr_lock, MA_OWNED);
mtx_assert(&atrtc_time_lock, MA_OWNED);
error = efi_enter();
if (error != 0)
return (error);
@ -462,9 +463,9 @@ efi_get_time(struct efi_tm *tm)
if (efi_runtime == NULL)
return (ENXIO);
mtx_lock(&resettodr_lock);
mtx_lock(&atrtc_time_lock);
error = efi_get_time_locked(tm);
mtx_unlock(&resettodr_lock);
mtx_unlock(&atrtc_time_lock);
return (error);
}
@ -487,7 +488,7 @@ efi_set_time_locked(struct efi_tm *tm)
efi_status status;
int error;
mtx_assert(&resettodr_lock, MA_OWNED);
mtx_assert(&atrtc_time_lock, MA_OWNED);
error = efi_enter();
if (error != 0)
return (error);
@ -504,9 +505,9 @@ efi_set_time(struct efi_tm *tm)
if (efi_runtime == NULL)
return (ENXIO);
mtx_lock(&resettodr_lock);
mtx_lock(&atrtc_time_lock);
error = efi_set_time_locked(tm);
mtx_unlock(&resettodr_lock);
mtx_unlock(&atrtc_time_lock);
return (error);
}

1
sys/isa/rtc.h
View File

@ -113,6 +113,7 @@
#ifdef _KERNEL
extern struct mtx clock_lock;
extern struct mtx atrtc_time_lock;
extern int atrtcclock_disable;
int rtcin(int reg);
void atrtc_restore(void);

14
sys/x86/isa/atrtc.c
View File

@ -53,9 +53,17 @@ __FBSDID("$FreeBSD$");
#include <machine/intr_machdep.h>
#include "clock_if.h"
/*
* clock_lock protects low-level access to individual hardware registers.
* atrtc_time_lock protects the entire sequence of accessing multiple registers
* to read or write the date and time.
*/
#define RTC_LOCK do { if (!kdb_active) mtx_lock_spin(&clock_lock); } while (0)
#define RTC_UNLOCK do { if (!kdb_active) mtx_unlock_spin(&clock_lock); } while (0)
struct mtx atrtc_time_lock;
MTX_SYSINIT(atrtc_lock_init, &atrtc_time_lock, "atrtc", MTX_DEF);
int atrtcclock_disable = 0;
static int rtc_reg = -1;
@ -163,6 +171,8 @@ atrtc_set(struct timespec *ts)
clock_ts_to_ct(ts, &ct);
mtx_lock(&atrtc_time_lock);
/* Disable RTC updates and interrupts. */
writertc(RTC_STATUSB, RTCSB_HALT | RTCSB_24HR);
@ -181,6 +191,8 @@ atrtc_set(struct timespec *ts)
/* Re-enable RTC updates and interrupts. */
writertc(RTC_STATUSB, rtc_statusb);
rtcin(RTC_INTR);
mtx_unlock(&atrtc_time_lock);
}
/**********************************************************************
@ -352,6 +364,7 @@ atrtc_gettime(device_t dev, struct timespec *ts)
* to make sure that no more than 240us pass after we start reading,
* and try again if so.
*/
mtx_lock(&atrtc_time_lock);
while (rtcin(RTC_STATUSA) & RTCSA_TUP)
continue;
critical_enter();
@ -369,6 +382,7 @@ atrtc_gettime(device_t dev, struct timespec *ts)
ct.year += (ct.year < 80 ? 2000 : 1900);
#endif
critical_exit();
mtx_unlock(&atrtc_time_lock);
/* Set dow = -1 because some clocks don't set it correctly. */
ct.dow = -1;
return (clock_ct_to_ts(&ct, ts));