Add const delcarations where possible to make clear that the call chains
are not permitted to write to the structure.
It is not expected to improve generated code; the purpose is to document
the rules for who's allowed to modify the timekeeper state (and must
hold the associated locks) more clearly.
There are two code paths affected:
- update_vsyscall() (and update_vsyscall_old(), if used)
- update_pvclock_gtod() and the functions notified
This touches arch code that I have not tested, but only in a very safe
way: to add const declarations whose only effect is to add compile-time
complaints.
Signed-off-by: George Spelvin <li...@horizon.com>
---
One style issue: Some people prefer "const struct timekeeper *", when
I'm in the habit of writing "struct timekeeper const *". This is due
to an example I had pointed out to me:
typedef char *charp;
const char *a;
char const *b;
char * const c;
const charp d;
charp const e;
Which of these variables are the same type? The answer is that a and b
are writable pointers to const chars, while c through e are const pointers
to writeable chars. But if you're in the habit of writing const first,
a and d are easy to confuse. If you get in the habit of writing const
last, e looks like c, which is correct. Due to the typedef, there's
no way write a declaration with the const "between the char and the *"
that looks like b.
I found this persuasive, and have adopted the style. If it causes
violent reactions, I can change.
arch/arm64/kernel/vdso.c | 2 +-
arch/ia64/kernel/time.c | 2 +-
arch/powerpc/kernel/time.c | 2 +-
arch/s390/kernel/time.c | 2 +-
arch/tile/kernel/time.c | 2 +-
arch/x86/kernel/vsyscall_gtod.c | 2 +-
arch/x86/kvm/x86.c | 4 ++--
include/linux/timekeeper_internal.h | 10 +++++-----
kernel/time/timekeeping.c | 8 ++++----
9 files changed, 17 insertions(+), 17 deletions(-)
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 50384fec56..dafdc36845 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -208,7 +208,7 @@ struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
/*
* Update the vDSO data page to keep in sync with kernel timekeeping.
*/
-void update_vsyscall(struct timekeeper *tk)
+void update_vsyscall(struct timekeeper const *tk)
{
struct timespec xtime_coarse;
u32 use_syscall = strcmp(tk->clock->name, "arch_sys_counter");
diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index 71c52bc7c2..353d5847f1 100644
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -440,7 +440,7 @@ void update_vsyscall_tz(void)
{
}
-void update_vsyscall_old(struct timespec *wall, struct timespec *wtm,
+void update_vsyscall_old(struct timespec *wall, struct timespec const *wtm,
struct clocksource *c, u32 mult)
{
write_seqcount_begin(&fsyscall_gtod_data.seq);
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 122a580f73..42ffd2309d 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -740,7 +740,7 @@ static cycle_t timebase_read(struct clocksource *cs)
return (cycle_t)get_tb();
}
-void update_vsyscall_old(struct timespec *wall_time, struct timespec *wtm,
+void update_vsyscall_old(struct timespec *wall_time, struct timespec const
*wtm,
struct clocksource *clock, u32 mult)
{
u64 new_tb_to_xs, new_stamp_xsec;
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 386d37a228..ea1c8d3137 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -210,7 +210,7 @@ struct clocksource * __init clocksource_default_clock(void)
return &clocksource_tod;
}
-void update_vsyscall(struct timekeeper *tk)
+void update_vsyscall(struct timekeeper const *tk)
{
u64 nsecps;
diff --git a/arch/tile/kernel/time.c b/arch/tile/kernel/time.c
index 462dcd0c17..7202570ad8 100644
--- a/arch/tile/kernel/time.c
+++ b/arch/tile/kernel/time.c
@@ -258,7 +258,7 @@ void update_vsyscall_tz(void)
++vdso_data->tz_update_count;
}
-void update_vsyscall(struct timekeeper *tk)
+void update_vsyscall(struct timekeeper const *tk)
{
struct timespec wall_time = tk_xtime(tk);
struct timespec *wtm = &tk->wall_to_monotonic;
diff --git a/arch/x86/kernel/vsyscall_gtod.c b/arch/x86/kernel/vsyscall_gtod.c
index f9c6e56e14..fa12766b38 100644
--- a/arch/x86/kernel/vsyscall_gtod.c
+++ b/arch/x86/kernel/vsyscall_gtod.c
@@ -24,7 +24,7 @@ void update_vsyscall_tz(void)
vsyscall_gtod_data.tz_dsttime = sys_tz.tz_dsttime;
}
-void update_vsyscall(struct timekeeper *tk)
+void update_vsyscall(struct timekeeper const *tk)
{
struct vsyscall_gtod_data *vdata = &vsyscall_gtod_data;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8b8fc0b792..0c42561f52 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1003,7 +1003,7 @@ struct pvclock_gtod_data {
static struct pvclock_gtod_data pvclock_gtod_data;
-static void update_pvclock_gtod(struct timekeeper *tk)
+static void update_pvclock_gtod(struct timekeeper const *tk)
{
struct pvclock_gtod_data *vdata = &pvclock_gtod_data;
@@ -5552,7 +5552,7 @@ static int pvclock_gtod_notify(struct notifier_block *nb,
unsigned long unused,
void *priv)
{
struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
- struct timekeeper *tk = priv;
+ struct timekeeper const *tk = priv;
update_pvclock_gtod(tk);
diff --git a/include/linux/timekeeper_internal.h
b/include/linux/timekeeper_internal.h
index c1825eb436..96e39501d8 100644
--- a/include/linux/timekeeper_internal.h
+++ b/include/linux/timekeeper_internal.h
@@ -71,7 +71,7 @@ struct timekeeper {
};
-static inline struct timespec tk_xtime(struct timekeeper *tk)
+static inline struct timespec tk_xtime(struct timekeeper const *tk)
{
struct timespec ts;
@@ -83,16 +83,16 @@ static inline struct timespec tk_xtime(struct timekeeper
*tk)
#ifdef CONFIG_GENERIC_TIME_VSYSCALL
-extern void update_vsyscall(struct timekeeper *tk);
+extern void update_vsyscall(struct timekeeper const *tk);
extern void update_vsyscall_tz(void);
#elif defined(CONFIG_GENERIC_TIME_VSYSCALL_OLD)
-extern void update_vsyscall_old(struct timespec *ts, struct timespec *wtm,
+extern void update_vsyscall_old(struct timespec *ts, struct timespec const
*wtm,
struct clocksource *c, u32 mult);
extern void update_vsyscall_tz(void);
-static inline void update_vsyscall(struct timekeeper *tk)
+static inline void update_vsyscall(struct timekeeper const *tk)
{
struct timespec xt;
@@ -102,7 +102,7 @@ static inline void update_vsyscall(struct timekeeper *tk)
#else
-static inline void update_vsyscall(struct timekeeper *tk)
+static inline void update_vsyscall(struct timekeeper const *tk)
{
}
static inline void update_vsyscall_tz(void)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 14e703e5bd..2e0fb0f617 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -165,7 +165,7 @@ u32 get_arch_timeoffset(void)
static inline u32 get_arch_timeoffset(void) { return 0; }
#endif
-static inline s64 timekeeping_get_ns(struct timekeeper *tk)
+static inline s64 timekeeping_get_ns(struct timekeeper const *tk)
{
cycle_t cycle_now, cycle_delta;
struct clocksource *clock;
@@ -185,7 +185,7 @@ static inline s64 timekeeping_get_ns(struct timekeeper *tk)
return nsec + get_arch_timeoffset();
}
-static inline s64 timekeeping_get_ns_raw(struct timekeeper *tk)
+static inline s64 timekeeping_get_ns_raw(struct timekeeper const *tk)
{
cycle_t cycle_now, cycle_delta;
struct clocksource *clock;
@@ -207,9 +207,9 @@ static inline s64 timekeeping_get_ns_raw(struct timekeeper
*tk)
static RAW_NOTIFIER_HEAD(pvclock_gtod_chain);
-static void update_pvclock_gtod(struct timekeeper *tk, bool was_set)
+static void update_pvclock_gtod(struct timekeeper const *tk, bool was_set)
{
- raw_notifier_call_chain(&pvclock_gtod_chain, was_set, tk);
+ raw_notifier_call_chain(&pvclock_gtod_chain, was_set, (void *)tk);
}
/**
--
1.9.2
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
