From 1c0c172695a42a11ca7206283b4f1d6a486d05ac Mon Sep 17 00:00:00 2001 From: Keir Fraser Date: Wed, 28 Nov 2007 12:40:57 +0000 Subject: [PATCH] [Mini-OS] Make gnttab allocation/free safe Add a semaphore to protect gnttab_list from exhaustion, and disable callbacks during allocation/free. Fix the network frontend accordingly. Signed-off-by: Samuel Thibault --- extras/mini-os/gnttab.c | 14 ++++++++++++-- extras/mini-os/netfront.c | 6 ++++-- 2 files changed, 16 insertions(+), 4 deletions(-) diff --git a/extras/mini-os/gnttab.c b/extras/mini-os/gnttab.c index b22f51ceae..5c2dcea863 100644 --- a/extras/mini-os/gnttab.c +++ b/extras/mini-os/gnttab.c @@ -18,6 +18,7 @@ #include #include #include +#include #define NR_RESERVED_ENTRIES 8 @@ -31,20 +32,29 @@ static grant_entry_t *gnttab_table; static grant_ref_t gnttab_list[NR_GRANT_ENTRIES]; +static __DECLARE_SEMAPHORE_GENERIC(gnttab_sem, NR_GRANT_ENTRIES); static void put_free_entry(grant_ref_t ref) { + unsigned long flags; + local_irq_save(flags); gnttab_list[ref] = gnttab_list[0]; gnttab_list[0] = ref; - + local_irq_restore(flags); + up(&gnttab_sem); } static grant_ref_t get_free_entry(void) { - unsigned int ref = gnttab_list[0]; + unsigned int ref; + unsigned long flags; + down(&gnttab_sem); + local_irq_save(flags); + ref = gnttab_list[0]; gnttab_list[0] = gnttab_list[ref]; + local_irq_restore(flags); return ref; } diff --git a/extras/mini-os/netfront.c b/extras/mini-os/netfront.c index fc1e9ab357..4341168652 100644 --- a/extras/mini-os/netfront.c +++ b/extras/mini-os/netfront.c @@ -147,6 +147,7 @@ moretodo: struct net_buffer* buf = &rx_buffers[id]; void* page = buf->page; + /* We are sure to have free gnttab entries since they got released above */ buf->gref = req->gref = gnttab_grant_access(0,virt_to_mfn(page),0); @@ -436,8 +437,9 @@ void netfront_xmit(unsigned char* data,int len) down(&tx_sem); local_irq_save(flags); - id = get_id_from_freelist(tx_freelist); + local_irq_restore(flags); + buf = &tx_buffers[id]; page = buf->page; @@ -461,7 +463,7 @@ void netfront_xmit(unsigned char* data,int len) if(notify) notify_remote_via_evtchn(info->evtchn); + local_irq_save(flags); network_tx_buf_gc(); - local_irq_restore(flags); } -- 2.30.2