Hi,
Before converting bpf(4) from using ticks to using real units of time
we need to serialize BIOCGRTIMEOUT and BIOCSRTIMEOUT. Neither
operation is atomic so we need to use the per-descriptor mutex when
reading or writing the bd_rtout member.
While here we can start annotating the locking for struct members in
bpfdesc.h, too.
ok?
Index: bpf.c
===================================================================
RCS file: /cvs/src/sys/net/bpf.c,v
retrieving revision 1.193
diff -u -p -r1.193 bpf.c
--- bpf.c 4 Nov 2020 04:40:13 -0000 1.193
+++ bpf.c 10 Dec 2020 17:24:43 -0000
@@ -873,9 +873,11 @@ bpfioctl(dev_t dev, u_long cmd, caddr_t
break;
}
rtout += tv->tv_usec / tick;
+ mtx_enter(&d->bd_mtx);
d->bd_rtout = rtout;
if (d->bd_rtout == 0 && tv->tv_usec != 0)
d->bd_rtout = 1;
+ mtx_leave(&d->bd_mtx);
break;
}
@@ -886,8 +888,10 @@ bpfioctl(dev_t dev, u_long cmd, caddr_t
{
struct timeval *tv = (struct timeval *)addr;
+ mtx_enter(&d->bd_mtx);
tv->tv_sec = d->bd_rtout / hz;
tv->tv_usec = (d->bd_rtout % hz) * tick;
+ mtx_leave(&d->bd_mtx);
break;
}
Index: bpfdesc.h
===================================================================
RCS file: /cvs/src/sys/net/bpfdesc.h,v
retrieving revision 1.41
diff -u -p -r1.41 bpfdesc.h
--- bpfdesc.h 13 May 2020 21:34:37 -0000 1.41
+++ bpfdesc.h 10 Dec 2020 17:24:43 -0000
@@ -42,6 +42,13 @@
#ifdef _KERNEL
+/*
+ * Locks used to protect struct members in this file:
+ *
+ * I immutable after initialization
+ * m the per-descriptor mutex (bpf_d.bd_mtx)
+ */
+
struct bpf_program_smr {
struct bpf_program bps_bf;
struct smr_entry bps_smr;
@@ -72,7 +79,7 @@ struct bpf_d {
int bd_in_uiomove; /* for debugging purpose */
struct bpf_if *bd_bif; /* interface descriptor */
- u_long bd_rtout; /* Read timeout in 'ticks' */
+ u_long bd_rtout; /* [m] Read timeout in 'ticks' */
u_long bd_rdStart; /* when the read started */
int bd_rnonblock; /* true if nonblocking reads are set */
struct bpf_program_smr
