diff options
author | Ed Schouten <ed@FreeBSD.org> | 2009-11-03 21:06:19 +0000 |
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committer | Ed Schouten <ed@FreeBSD.org> | 2009-11-03 21:06:19 +0000 |
commit | ca1d2f657ac8942f180f7d1ab328400ae8524bf0 (patch) | |
tree | b1831228fc9c75d881dcef9aa5a2a860de274f46 /sys/kern/subr_log.c | |
parent | 21293e70168c37da3ea5095339ff18c3dc867f65 (diff) | |
download | src-ca1d2f657ac8942f180f7d1ab328400ae8524bf0.tar.gz src-ca1d2f657ac8942f180f7d1ab328400ae8524bf0.zip |
Make /dev/klog and kern.msgbuf* MPSAFE.
Normally msgbufp is locked using Giant. Switch it to use the
msgbuf_lock. Instead of changing the tsleep() calls to msleep(), just
convert it to condvar(9).
In my opinion the locking around msgbuf_peekbytes() still remains
questionable. It looks like locks are dropped while performing copies of
multiple blocks to userspace, which may cause the msgbuf to be reset in
the mean time. At least getting it underneath from Giant should make it
a little easier for us to figure out how to solve that.
Reminded by: rdivacky
Notes
Notes:
svn path=/head/; revision=198860
Diffstat (limited to 'sys/kern/subr_log.c')
-rw-r--r-- | sys/kern/subr_log.c | 73 |
1 files changed, 41 insertions, 32 deletions
diff --git a/sys/kern/subr_log.c b/sys/kern/subr_log.c index 01a3acc98519..972f9f941852 100644 --- a/sys/kern/subr_log.c +++ b/sys/kern/subr_log.c @@ -53,7 +53,6 @@ __FBSDID("$FreeBSD$"); #define LOG_RDPRI (PZERO + 1) #define LOG_ASYNC 0x04 -#define LOG_RDWAIT 0x08 static d_open_t logopen; static d_close_t logclose; @@ -65,7 +64,6 @@ static void logtimeout(void *arg); static struct cdevsw log_cdevsw = { .d_version = D_VERSION, - .d_flags = D_NEEDGIANT, .d_open = logopen, .d_close = logclose, .d_read = logread, @@ -81,7 +79,10 @@ static struct logsoftc { struct callout sc_callout; /* callout to wakeup syslog */ } logsoftc; -int log_open; /* also used in log() */ +int log_open; /* also used in log() */ +static struct cv log_wakeup; +struct mtx msgbuf_lock; +MTX_SYSINIT(msgbuf_lock, &msgbuf_lock, "msgbuf lock", MTX_DEF); /* Times per second to check for a pending syslog wakeup. */ static int log_wakeups_per_second = 5; @@ -92,17 +93,23 @@ SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW, static int logopen(struct cdev *dev, int flags, int mode, struct thread *td) { - if (log_open) - return (EBUSY); - log_open = 1; - callout_init(&logsoftc.sc_callout, 0); - fsetown(td->td_proc->p_pid, &logsoftc.sc_sigio); /* signal process only */ + if (log_wakeups_per_second < 1) { printf("syslog wakeup is less than one. Adjusting to 1.\n"); log_wakeups_per_second = 1; } + + mtx_lock(&msgbuf_lock); + if (log_open) { + mtx_unlock(&msgbuf_lock); + return (EBUSY); + } + log_open = 1; callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second, logtimeout, NULL); + mtx_unlock(&msgbuf_lock); + + fsetown(td->td_proc->p_pid, &logsoftc.sc_sigio); /* signal process only */ return (0); } @@ -111,10 +118,14 @@ static int logclose(struct cdev *dev, int flag, int mode, struct thread *td) { - log_open = 0; + funsetown(&logsoftc.sc_sigio); + + mtx_lock(&msgbuf_lock); callout_stop(&logsoftc.sc_callout); logsoftc.sc_state = 0; - funsetown(&logsoftc.sc_sigio); + log_open = 0; + mtx_unlock(&msgbuf_lock); + return (0); } @@ -124,32 +135,32 @@ logread(struct cdev *dev, struct uio *uio, int flag) { char buf[128]; struct msgbuf *mbp = msgbufp; - int error = 0, l, s; + int error = 0, l; - s = splhigh(); + mtx_lock(&msgbuf_lock); while (msgbuf_getcount(mbp) == 0) { if (flag & IO_NDELAY) { - splx(s); + mtx_unlock(&msgbuf_lock); return (EWOULDBLOCK); } - logsoftc.sc_state |= LOG_RDWAIT; - if ((error = tsleep(mbp, LOG_RDPRI | PCATCH, "klog", 0))) { - splx(s); + if ((error = cv_wait_sig(&log_wakeup, &msgbuf_lock)) != 0) { + mtx_unlock(&msgbuf_lock); return (error); } } - splx(s); - logsoftc.sc_state &= ~LOG_RDWAIT; while (uio->uio_resid > 0) { l = imin(sizeof(buf), uio->uio_resid); l = msgbuf_getbytes(mbp, buf, l); if (l == 0) break; + mtx_unlock(&msgbuf_lock); error = uiomove(buf, l, uio); - if (error) - break; + if (error || uio->uio_resid == 0) + return (error); + mtx_lock(&msgbuf_lock); } + mtx_unlock(&msgbuf_lock); return (error); } @@ -157,18 +168,16 @@ logread(struct cdev *dev, struct uio *uio, int flag) static int logpoll(struct cdev *dev, int events, struct thread *td) { - int s; int revents = 0; - s = splhigh(); - if (events & (POLLIN | POLLRDNORM)) { + mtx_lock(&msgbuf_lock); if (msgbuf_getcount(msgbufp) > 0) revents |= events & (POLLIN | POLLRDNORM); else selrecord(td, &logsoftc.sc_selp); + mtx_unlock(&msgbuf_lock); } - splx(s); return (revents); } @@ -183,20 +192,16 @@ logtimeout(void *arg) log_wakeups_per_second = 1; } if (msgbuftrigger == 0) { - callout_reset(&logsoftc.sc_callout, - hz / log_wakeups_per_second, logtimeout, NULL); + callout_schedule(&logsoftc.sc_callout, + hz / log_wakeups_per_second); return; } msgbuftrigger = 0; selwakeuppri(&logsoftc.sc_selp, LOG_RDPRI); if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL) pgsigio(&logsoftc.sc_sigio, SIGIO, 0); - if (logsoftc.sc_state & LOG_RDWAIT) { - wakeup(msgbufp); - logsoftc.sc_state &= ~LOG_RDWAIT; - } - callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second, - logtimeout, NULL); + cv_broadcastpri(&log_wakeup, LOG_RDPRI); + callout_schedule(&logsoftc.sc_callout, hz / log_wakeups_per_second); } /*ARGSUSED*/ @@ -215,10 +220,12 @@ logioctl(struct cdev *dev, u_long com, caddr_t data, int flag, struct thread *td break; case FIOASYNC: + mtx_lock(&msgbuf_lock); if (*(int *)data) logsoftc.sc_state |= LOG_ASYNC; else logsoftc.sc_state &= ~LOG_ASYNC; + mtx_unlock(&msgbuf_lock); break; case FIOSETOWN: @@ -247,6 +254,8 @@ static void log_drvinit(void *unused) { + cv_init(&log_wakeup, "klog"); + callout_init_mtx(&logsoftc.sc_callout, &msgbuf_lock, 0); make_dev(&log_cdevsw, 0, UID_ROOT, GID_WHEEL, 0600, "klog"); } |