From: Jan Kiszka Date: Mon, 8 Feb 2010 10:12:15 +0000 (+0000) Subject: CAPI: Rework application locking X-Git-Tag: v2.6.34-rc1~233^2~273 X-Git-Url: http://ftp.safe.ca/?p=safe%2Fjmp%2Flinux-2.6;a=commitdiff_plain;h=88c896ef87fd0dd4dbf36e8e86e019c74b1f6649 CAPI: Rework application locking Drop the application rw-lock in favour of RCU. This synchronizes capi20_release against capi_ctr_handle_message which may dereference an application from (soft-)IRQ context. Any other access to the application list is now protected by the capi_controller_lock as well. This also allows to safely inspect applications for /proc dumping by holding capi_controller_lock. At this chance, drop some useless release_in_progress checks where we obtained the application pointer from the list (which becomes NULL on release_in_progress). Signed-off-by: Jan Kiszka Signed-off-by: David S. Miller --- diff --git a/drivers/isdn/capi/kcapi.c b/drivers/isdn/capi/kcapi.c index a99f7e3..0b4c8a7 100644 --- a/drivers/isdn/capi/kcapi.c +++ b/drivers/isdn/capi/kcapi.c @@ -34,6 +34,7 @@ #include #endif #include +#include static int showcapimsgs = 0; @@ -64,8 +65,6 @@ DEFINE_MUTEX(capi_drivers_lock); struct capi_ctr *capi_controller[CAPI_MAXCONTR]; DEFINE_MUTEX(capi_controller_lock); -static DEFINE_RWLOCK(application_lock); - struct capi20_appl *capi_applications[CAPI_MAXAPPL]; static int ncontrollers; @@ -103,7 +102,7 @@ static inline struct capi20_appl *get_capi_appl_by_nr(u16 applid) if (applid - 1 >= CAPI_MAXAPPL) return NULL; - return capi_applications[applid - 1]; + return rcu_dereference(capi_applications[applid - 1]); } /* -------- util functions ------------------------------------ */ @@ -186,7 +185,7 @@ static void notify_up(u32 contr) for (applid = 1; applid <= CAPI_MAXAPPL; applid++) { ap = get_capi_appl_by_nr(applid); - if (!ap || ap->release_in_progress) + if (!ap) continue; register_appl(ctr, applid, &ap->rparam); } @@ -216,7 +215,7 @@ static void ctr_down(struct capi_ctr *ctr, int new_state) for (applid = 1; applid <= CAPI_MAXAPPL; applid++) { ap = get_capi_appl_by_nr(applid); - if (ap && !ap->release_in_progress) + if (ap) capi_ctr_put(ctr); } @@ -336,7 +335,6 @@ void capi_ctr_handle_message(struct capi_ctr *ctr, u16 appl, struct capi20_appl *ap; int showctl = 0; u8 cmd, subcmd; - unsigned long flags; _cdebbuf *cdb; if (ctr->state != CAPI_CTR_RUNNING) { @@ -384,10 +382,10 @@ void capi_ctr_handle_message(struct capi_ctr *ctr, u16 appl, } - read_lock_irqsave(&application_lock, flags); + rcu_read_lock(); ap = get_capi_appl_by_nr(CAPIMSG_APPID(skb->data)); - if ((!ap) || (ap->release_in_progress)) { - read_unlock_irqrestore(&application_lock, flags); + if (!ap) { + rcu_read_unlock(); cdb = capi_message2str(skb->data); if (cdb) { printk(KERN_ERR "kcapi: handle_message: applid %d state released (%s)\n", @@ -401,7 +399,7 @@ void capi_ctr_handle_message(struct capi_ctr *ctr, u16 appl, } skb_queue_tail(&ap->recv_queue, skb); schedule_work(&ap->recv_work); - read_unlock_irqrestore(&application_lock, flags); + rcu_read_unlock(); return; @@ -656,40 +654,35 @@ u16 capi20_register(struct capi20_appl *ap) { int i; u16 applid; - unsigned long flags; DBG(""); if (ap->rparam.datablklen < 128) return CAPI_LOGBLKSIZETOSMALL; - write_lock_irqsave(&application_lock, flags); + ap->nrecvctlpkt = 0; + ap->nrecvdatapkt = 0; + ap->nsentctlpkt = 0; + ap->nsentdatapkt = 0; + mutex_init(&ap->recv_mtx); + skb_queue_head_init(&ap->recv_queue); + INIT_WORK(&ap->recv_work, recv_handler); + ap->release_in_progress = 0; + + mutex_lock(&capi_controller_lock); for (applid = 1; applid <= CAPI_MAXAPPL; applid++) { if (capi_applications[applid - 1] == NULL) break; } if (applid > CAPI_MAXAPPL) { - write_unlock_irqrestore(&application_lock, flags); + mutex_unlock(&capi_controller_lock); return CAPI_TOOMANYAPPLS; } ap->applid = applid; capi_applications[applid - 1] = ap; - ap->nrecvctlpkt = 0; - ap->nrecvdatapkt = 0; - ap->nsentctlpkt = 0; - ap->nsentdatapkt = 0; - mutex_init(&ap->recv_mtx); - skb_queue_head_init(&ap->recv_queue); - INIT_WORK(&ap->recv_work, recv_handler); - ap->release_in_progress = 0; - - write_unlock_irqrestore(&application_lock, flags); - - mutex_lock(&capi_controller_lock); - for (i = 0; i < CAPI_MAXCONTR; i++) { if (!capi_controller[i] || capi_controller[i]->state != CAPI_CTR_RUNNING) @@ -721,16 +714,15 @@ EXPORT_SYMBOL(capi20_register); u16 capi20_release(struct capi20_appl *ap) { int i; - unsigned long flags; DBG("applid %#x", ap->applid); - write_lock_irqsave(&application_lock, flags); + mutex_lock(&capi_controller_lock); + ap->release_in_progress = 1; capi_applications[ap->applid - 1] = NULL; - write_unlock_irqrestore(&application_lock, flags); - mutex_lock(&capi_controller_lock); + synchronize_rcu(); for (i = 0; i < CAPI_MAXCONTR; i++) { if (!capi_controller[i] || diff --git a/drivers/isdn/capi/kcapi_proc.c b/drivers/isdn/capi/kcapi_proc.c index 3e6e17a..ea2dff6 100644 --- a/drivers/isdn/capi/kcapi_proc.c +++ b/drivers/isdn/capi/kcapi_proc.c @@ -139,9 +139,11 @@ static const struct file_operations proc_contrstats_ops = { // applid nrecvctlpkt nrecvdatapkt nsentctlpkt nsentdatapkt // --------------------------------------------------------------------------- -static void * -applications_start(struct seq_file *seq, loff_t *pos) +static void *applications_start(struct seq_file *seq, loff_t *pos) + __acquires(capi_controller_lock) { + mutex_lock(&capi_controller_lock); + if (*pos < CAPI_MAXAPPL) return &capi_applications[*pos]; @@ -158,9 +160,10 @@ applications_next(struct seq_file *seq, void *v, loff_t *pos) return NULL; } -static void -applications_stop(struct seq_file *seq, void *v) +static void applications_stop(struct seq_file *seq, void *v) + __releases(capi_controller_lock) { + mutex_unlock(&capi_controller_lock); } static int