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timerfd: Define a locking regime

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Define a locking regime for the members of struct timerfd and document
    it so future code can follow the standard. The lock legend can be found
    in a comment above struct timerfd.

    Additionally,
    * Add assertions based on locking regime.
    * Fill kn_data with the expiration count when EVFILT_READ is triggered.
    * Report st_ctim for stat(2).
    * Check if file has f_type == DTYPE_TIMERFD before assigning timerfd
      pointer to f_data.

MFC After: 3 days
Reviewed by:	imp, kib, markj
Differential Revision:	https://reviews.freebsd.org/D41600

(cherry picked from commit a1f506156c4db885d3cc177c93e9c8a28d535d30)
This commit is contained in:
Jake Freeland 2023-09-17 09:01:46 -06:00 committed by Warner Losh
parent a87dddf39e
commit d00e6d8774
1 changed files with 35 additions and 26 deletions
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61
sys/kern/sys_timerfd.c
View file

@ -73,28 +73,36 @@ static struct unrhdr64 tfdino_unr;
#define TFD_CANCELED 4 /* Jumped, CANCEL_ON_SET=true. */
#define TFD_JUMPED (TFD_ZREAD | TFD_CANCELED)
/*
* One structure allocated per timerfd descriptor.
*
* Locking semantics:
* (t) locked by tfd_lock mtx
* (l) locked by timerfd_list_lock sx
* (c) const until freeing
*/
struct timerfd {
/* User specified. */
struct itimerspec tfd_time; /* tfd timer */
clockid_t tfd_clockid; /* timing base */
int tfd_flags; /* creation flags */
int tfd_timflags; /* timer flags */
struct itimerspec tfd_time; /* (t) tfd timer */
clockid_t tfd_clockid; /* (c) timing base */
int tfd_flags; /* (c) creation flags */
int tfd_timflags; /* (t) timer flags */
/* Used internally. */
timerfd_t tfd_count; /* expiration count since last read */
bool tfd_expired; /* true upon initial expiration */
struct mtx tfd_lock; /* mtx lock */
struct callout tfd_callout; /* expiration notification */
struct selinfo tfd_sel; /* I/O alerts */
struct timespec tfd_boottim; /* cached boottime */
int tfd_jumped; /* timer jump status */
LIST_ENTRY(timerfd) entry; /* entry in list */
timerfd_t tfd_count; /* (t) expiration count since read */
bool tfd_expired; /* (t) true upon initial expiration */
struct mtx tfd_lock; /* tfd mtx lock */
struct callout tfd_callout; /* (t) expiration notification */
struct selinfo tfd_sel; /* (t) I/O alerts */
struct timespec tfd_boottim; /* (t) cached boottime */
int tfd_jumped; /* (t) timer jump status */
LIST_ENTRY(timerfd) entry; /* (l) entry in list */
/* For stat(2). */
ino_t tfd_ino; /* inode number */
struct timespec tfd_atim; /* time of last read */
struct timespec tfd_mtim; /* time of last settime */
struct timespec tfd_birthtim; /* creation time */
ino_t tfd_ino; /* (c) inode number */
struct timespec tfd_atim; /* (t) time of last read */
struct timespec tfd_mtim; /* (t) time of last settime */
struct timespec tfd_birthtim; /* (c) creation time */
};
static void
@ -109,6 +117,7 @@ static inline void
timerfd_getboottime(struct timespec *ts)
{
struct timeval tv;
getboottime(&tv);
TIMEVAL_TO_TIMESPEC(&tv, ts);
}
@ -274,6 +283,8 @@ filt_timerfdread(struct knote *kn, long hint)
{
struct timerfd *tfd = kn->kn_hook;
mtx_assert(&tfd->tfd_lock, MA_OWNED);
kn->kn_data = (int64_t)tfd->tfd_count;
return (tfd->tfd_count > 0);
}
@ -308,13 +319,13 @@ timerfd_stat(struct file *fp, struct stat *sb, struct ucred *active_cred)
sb->st_uid = fp->f_cred->cr_uid;
sb->st_gid = fp->f_cred->cr_gid;
sb->st_blksize = PAGE_SIZE;
mtx_lock(&tfd->tfd_lock);
sb->st_ino = tfd->tfd_ino;
sb->st_atim = tfd->tfd_atim;
sb->st_mtim = tfd->tfd_mtim;
sb->st_birthtim = tfd->tfd_birthtim;
mtx_unlock(&tfd->tfd_lock);
sb->st_ctim = sb->st_mtim;
sb->st_ino = tfd->tfd_ino;
sb->st_birthtim = tfd->tfd_birthtim;
return (0);
}
@ -342,15 +353,12 @@ static int
timerfd_fill_kinfo(struct file *fp, struct kinfo_file *kif,
struct filedesc *fdp)
{
struct timerfd *tfd = fp->f_data;
kif->kf_type = KF_TYPE_TIMERFD;
mtx_lock(&tfd->tfd_lock);
kif->kf_un.kf_timerfd.kf_timerfd_clockid = tfd->tfd_clockid;
kif->kf_un.kf_timerfd.kf_timerfd_flags = tfd->tfd_flags;
kif->kf_un.kf_timerfd.kf_timerfd_addr = (uintptr_t)tfd;
mtx_unlock(&tfd->tfd_lock);
return (0);
}
@ -376,6 +384,7 @@ timerfd_curval(struct timerfd *tfd, struct itimerspec *old_value)
{
struct timespec curr_value;
mtx_assert(&tfd->tfd_lock, MA_OWNED);
*old_value = tfd->tfd_time;
if (timespecisset(&tfd->tfd_time.it_value)) {
nanouptime(&curr_value);
@ -472,11 +481,11 @@ kern_timerfd_gettime(struct thread *td, int fd, struct itimerspec *curr_value)
error = fget(td, fd, &cap_write_rights, &fp);
if (error != 0)
return (error);
tfd = fp->f_data;
if (tfd == NULL || fp->f_type != DTYPE_TIMERFD) {
if (fp->f_type != DTYPE_TIMERFD) {
fdrop(fp, td);
return (EINVAL);
}
tfd = fp->f_data;
mtx_lock(&tfd->tfd_lock);
timerfd_curval(tfd, curr_value);
@ -504,11 +513,11 @@ kern_timerfd_settime(struct thread *td, int fd, int flags,
error = fget(td, fd, &cap_write_rights, &fp);
if (error != 0)
return (error);
tfd = fp->f_data;
if (tfd == NULL || fp->f_type != DTYPE_TIMERFD) {
if (fp->f_type != DTYPE_TIMERFD) {
fdrop(fp, td);
return (EINVAL);
}
tfd = fp->f_data;
mtx_lock(&tfd->tfd_lock);
getnanotime(&tfd->tfd_mtim);