On Fri, 2018-09-21 at 18:05 -0500, Benjamin Marzinski wrote: > tur_devt() locks ct->lock. However, it is ocassionally called while > ct->lock is already locked. In reality, there is no reason why we > need > to lock all the accesses to ct->devt. The tur checker only needs to > write to this variable one time, when it first gets the file > descripter > that it is checking. It also never uses ct->devt directly. Instead, > it > always graps the major and minor, and turns them into a string. This > patch changes ct->devt into that string, and sets it in > libcheck_init() > when it is first initializing the checker context. After that, ct- > >devt > is only ever read.
I like the lock removal a lot, but not so much the conversion into a string. Why not keep the dev_t? Or maybe even easier, the other way around: why don't we make it a char* and simply set checker->dev_t = &pp->dev_t? Regards, Martin > > Cc: Bart Van Assche <[email protected]>4 > Signed-off-by: Benjamin Marzinski <[email protected]> > --- > libmultipath/checkers/tur.c | 55 +++++++++++++-------------------- > ------------ > 1 file changed, 16 insertions(+), 39 deletions(-) > > diff --git a/libmultipath/checkers/tur.c > b/libmultipath/checkers/tur.c > index 275541f..d173648 100644 > --- a/libmultipath/checkers/tur.c > +++ b/libmultipath/checkers/tur.c > @@ -37,36 +37,24 @@ > #define MSG_TUR_FAILED "tur checker failed to initialize" > > struct tur_checker_context { > - dev_t devt; > + char devt[32]; > int state; > - int running; > + int running; /* uatomic access only */ > int fd; > unsigned int timeout; > time_t time; > pthread_t thread; > pthread_mutex_t lock; > pthread_cond_t active; > - int holders; > + int holders; /* uatomic access only */ > char message[CHECKER_MSG_LEN]; > }; > > -static const char *tur_devt(char *devt_buf, int size, > - struct tur_checker_context *ct) > -{ > - dev_t devt; > - > - pthread_mutex_lock(&ct->lock); > - devt = ct->devt; > - pthread_mutex_unlock(&ct->lock); > - > - snprintf(devt_buf, size, "%d:%d", major(devt), minor(devt)); > - return devt_buf; > -} > - > int libcheck_init (struct checker * c) > { > struct tur_checker_context *ct; > pthread_mutexattr_t attr; > + struct stat sb; > > ct = malloc(sizeof(struct tur_checker_context)); > if (!ct) > @@ -81,6 +69,9 @@ int libcheck_init (struct checker * c) > pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE); > pthread_mutex_init(&ct->lock, &attr); > pthread_mutexattr_destroy(&attr); > + if (fstat(c->fd, &sb) == 0) > + snprintf(ct->devt, sizeof(ct->devt), "%d:%d", > major(sb.st_rdev), > + minor(sb.st_rdev)); > c->context = ct; > > return 0; > @@ -232,14 +223,12 @@ static void *tur_thread(void *ctx) > { > struct tur_checker_context *ct = ctx; > int state, running; > - char devt[32]; > > /* This thread can be canceled, so setup clean up */ > tur_thread_cleanup_push(ct); > rcu_register_thread(); > > - condlog(3, "%s: tur checker starting up", > - tur_devt(devt, sizeof(devt), ct)); > + condlog(3, "%s: tur checker starting up", ct->devt); > > /* TUR checker start up */ > pthread_mutex_lock(&ct->lock); > @@ -256,8 +245,8 @@ static void *tur_thread(void *ctx) > pthread_cond_signal(&ct->active); > pthread_mutex_unlock(&ct->lock); > > - condlog(3, "%s: tur checker finished, state %s", > - tur_devt(devt, sizeof(devt), ct), > checker_state_name(state)); > + condlog(3, "%s: tur checker finished, state %s", ct->devt, > + checker_state_name(state)); > > running = uatomic_xchg(&ct->running, 0); > if (!running) > @@ -305,20 +294,12 @@ int libcheck_check(struct checker * c) > { > struct tur_checker_context *ct = c->context; > struct timespec tsp; > - struct stat sb; > pthread_attr_t attr; > int tur_status, r; > - char devt[32]; > > if (!ct) > return PATH_UNCHECKED; > > - if (fstat(c->fd, &sb) == 0) { > - pthread_mutex_lock(&ct->lock); > - ct->devt = sb.st_rdev; > - pthread_mutex_unlock(&ct->lock); > - } > - > if (c->sync) > return tur_check(c->fd, c->timeout, > copy_msg_to_checker, c); > > @@ -327,8 +308,7 @@ int libcheck_check(struct checker * c) > */ > r = pthread_mutex_lock(&ct->lock); > if (r != 0) { > - condlog(2, "%s: tur mutex lock failed with %d", > - tur_devt(devt, sizeof(devt), ct), r); > + condlog(2, "%s: tur mutex lock failed with %d", ct- > >devt, r); > MSG(c, MSG_TUR_FAILED); > return PATH_WILD; > } > @@ -338,14 +318,12 @@ int libcheck_check(struct checker * c) > int running = uatomic_xchg(&ct->running, 0); > if (running) > pthread_cancel(ct->thread); > - condlog(3, "%s: tur checker timeout", > - tur_devt(devt, sizeof(devt), ct)); > + condlog(3, "%s: tur checker timeout", ct- > >devt); > ct->thread = 0; > MSG(c, MSG_TUR_TIMEOUT); > tur_status = PATH_TIMEOUT; > } else if (uatomic_read(&ct->running) != 0) { > - condlog(3, "%s: tur checker not finished", > - tur_devt(devt, sizeof(devt), > ct)); > + condlog(3, "%s: tur checker not finished", ct- > >devt); > tur_status = PATH_PENDING; > } else { > /* TUR checker done */ > @@ -361,7 +339,7 @@ int libcheck_check(struct checker * c) > if (ct->state == PATH_PENDING) { > pthread_mutex_unlock(&ct->lock); > condlog(3, "%s: tur thread not > responding", > - tur_devt(devt, sizeof(devt), > ct)); > + ct->devt); > return PATH_TIMEOUT; > } > } > @@ -381,7 +359,7 @@ int libcheck_check(struct checker * c) > ct->thread = 0; > pthread_mutex_unlock(&ct->lock); > condlog(3, "%s: failed to start tur thread, > using" > - " sync mode", tur_devt(devt, > sizeof(devt), ct)); > + " sync mode", ct->devt); > return tur_check(c->fd, c->timeout, > copy_msg_to_checker, c); > } > @@ -392,8 +370,7 @@ int libcheck_check(struct checker * c) > pthread_mutex_unlock(&ct->lock); > if (uatomic_read(&ct->running) != 0 && > (tur_status == PATH_PENDING || tur_status == > PATH_UNCHECKED)) { > - condlog(3, "%s: tur checker still running", > - tur_devt(devt, sizeof(devt), ct)); > + condlog(3, "%s: tur checker still running", ct- > >devt); > tur_status = PATH_PENDING; > } else { > int running = uatomic_xchg(&ct->running, 0); -- Dr. Martin Wilck <[email protected]>, Tel. +49 (0)911 74053 2107 SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg) -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
