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authorRickard Green <[email protected]>2010-08-19 18:57:03 +0200
committerRickard Green <[email protected]>2010-08-20 22:23:36 +0200
commit044c73a55dbc3223cc02c10e11fc7798bf41a242 (patch)
treeb1c67d3ad4fd8f86957a2e1049246699f2357089 /erts
parent6af9c31d7f25a653342cd40affe1bf764748c210 (diff)
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Fix race in erts_poll()
A race condition in erts_poll() could cause delay of poll for I/O.
Diffstat (limited to 'erts')
-rw-r--r--erts/emulator/sys/common/erl_poll.c39
1 files changed, 20 insertions, 19 deletions
diff --git a/erts/emulator/sys/common/erl_poll.c b/erts/emulator/sys/common/erl_poll.c
index 09fb6337f7..c17806d96c 100644
--- a/erts/emulator/sys/common/erl_poll.c
+++ b/erts/emulator/sys/common/erl_poll.c
@@ -286,7 +286,7 @@ struct ErtsPollSet_ {
ErtsPollSet next;
int internal_fd_limit;
ErtsFdStatus *fds_status;
- int no_of_user_fds;
+ erts_smp_atomic_t no_of_user_fds;
int fds_status_len;
#if ERTS_POLL_USE_KERNEL_POLL
int kp_fd;
@@ -852,7 +852,7 @@ write_batch_buf(ErtsPollSet ps, ErtsPollBatchBuf *bbp)
ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_USEFLBCK;
ASSERT(ps->fds_status[fd].used_events);
ps->fds_status[fd].used_events = 0;
- ps->no_of_user_fds--;
+ erts_smp_atomic_dec(&ps->no_of_user_fds);
update_fallback_pollset(ps, fd);
ASSERT(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK);
break;
@@ -902,11 +902,11 @@ batch_update_pollset(ErtsPollSet ps, int fd, ErtsPollBatchBuf *bbp)
events = ERTS_POLL_EV_E2N(ps->fds_status[fd].events);
if (!events) {
buf[buf_len].events = POLLREMOVE;
- ps->no_of_user_fds--;
+ erts_smp_atomic_dec(&ps->no_of_user_fds);
}
else if (!ps->fds_status[fd].used_events) {
buf[buf_len].events = events;
- ps->no_of_user_fds++;
+ erts_smp_atomic_inc(&ps->no_of_user_fds);
}
else {
if ((ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST)
@@ -996,12 +996,12 @@ batch_update_pollset(ErtsPollSet ps, int fd, ErtsPollBatchBuf *bbp)
}
if (used_events) {
if (!events) {
- ps->no_of_user_fds--;
+ erts_smp_atomic_dec(&ps->no_of_user_fds);
}
}
else {
if (events)
- ps->no_of_user_fds++;
+ erts_smp_atomic_inc(&ps->no_of_user_fds);
}
ASSERT((events & ~(ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT)) == 0);
ASSERT((used_events & ~(ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT)) == 0);
@@ -1075,7 +1075,7 @@ update_pollset(ErtsPollSet ps, int fd)
epe.data.fd = epe_templ.data.fd;
res = epoll_ctl(ps->kp_fd, EPOLL_CTL_DEL, fd, &epe);
} while (res != 0 && errno == EINTR);
- ps->no_of_user_fds--;
+ erts_smp_atomic_dec(&ps->no_of_user_fds);
ps->fds_status[fd].used_events = 0;
}
@@ -1083,11 +1083,11 @@ update_pollset(ErtsPollSet ps, int fd)
/* A note on EPOLL_CTL_DEL: linux kernel versions before 2.6.9
need a non-NULL event pointer even though it is ignored... */
op = EPOLL_CTL_DEL;
- ps->no_of_user_fds--;
+ erts_smp_atomic_dec(&ps->no_of_user_fds);
}
else if (!ps->fds_status[fd].used_events) {
op = EPOLL_CTL_ADD;
- ps->no_of_user_fds++;
+ erts_smp_atomic_inc(&ps->no_of_user_fds);
}
else {
op = EPOLL_CTL_MOD;
@@ -1137,7 +1137,7 @@ update_pollset(ErtsPollSet ps, int fd)
/* Fall through ... */
case EPOLL_CTL_ADD: {
ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_USEFLBCK;
- ps->no_of_user_fds--;
+ erts_smp_atomic_dec(&ps->no_of_user_fds);
#if ERTS_POLL_USE_CONCURRENT_UPDATE
if (!*update_fallback) {
*update_fallback = 1;
@@ -1225,7 +1225,7 @@ static int update_pollset(ErtsPollSet ps, int fd)
#if ERTS_POLL_USE_FALLBACK
ASSERT(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK);
#endif
- ps->no_of_user_fds--;
+ erts_smp_atomic_dec(&ps->no_of_user_fds);
last_pix = --ps->no_poll_fds;
if (pix != last_pix) {
/* Move last pix to this pix */
@@ -1252,7 +1252,7 @@ static int update_pollset(ErtsPollSet ps, int fd)
ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK)
|| fd == ps->kp_fd);
#endif
- ps->no_of_user_fds++;
+ erts_smp_atomic_inc(&ps->no_of_user_fds);
ps->fds_status[fd].pix = pix = ps->no_poll_fds++;
if (pix >= ps->poll_fds_len)
grow_poll_fds(ps, pix);
@@ -1303,7 +1303,7 @@ static int update_pollset(ErtsPollSet ps, int fd)
if (!ps->fds_status[fd].used_events) {
ASSERT(events);
- ps->no_of_user_fds++;
+ erts_smp_atomic_inc(&ps->no_of_user_fds);
#if ERTS_POLL_USE_FALLBACK
ps->no_select_fds++;
ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_INFLBCK;
@@ -1311,7 +1311,7 @@ static int update_pollset(ErtsPollSet ps, int fd)
}
else if (!events) {
ASSERT(ps->fds_status[fd].used_events);
- ps->no_of_user_fds--;
+ erts_smp_atomic_dec(&ps->no_of_user_fds);
ps->fds_status[fd].events = events;
#if ERTS_POLL_USE_FALLBACK
ps->no_select_fds--;
@@ -1912,7 +1912,8 @@ static ERTS_INLINE int
check_fd_events(ErtsPollSet ps, SysTimeval *tv, int max_res, int *ps_locked)
{
ASSERT(!*ps_locked);
- if (ps->no_of_user_fds == 0 && tv->tv_usec == 0 && tv->tv_sec == 0) {
+ if (erts_smp_atomic_read(&ps->no_of_user_fds) == 0
+ && tv->tv_usec == 0 && tv->tv_sec == 0) {
/* Nothing to poll and zero timeout; done... */
return 0;
}
@@ -1950,7 +1951,7 @@ check_fd_events(ErtsPollSet ps, SysTimeval *tv, int max_res, int *ps_locked)
* the maximum number of file descriptors in the poll set.
*/
struct dvpoll poll_res;
- int nfds = ps->no_of_user_fds;
+ int nfds = (int) erts_smp_atomic_read(&ps->no_of_user_fds);
#ifdef ERTS_SMP
nfds++; /* Wakeup pipe */
#endif
@@ -2228,7 +2229,7 @@ ERTS_POLL_EXPORT(erts_poll_create_pollset)(void)
ps->internal_fd_limit = 0;
ps->fds_status = NULL;
ps->fds_status_len = 0;
- ps->no_of_user_fds = 0;
+ erts_smp_atomic_init(&ps->no_of_user_fds, 0);
#if ERTS_POLL_USE_KERNEL_POLL
ps->kp_fd = -1;
#if ERTS_POLL_USE_EPOLL
@@ -2326,7 +2327,7 @@ ERTS_POLL_EXPORT(erts_poll_create_pollset)(void)
#if ERTS_POLL_USE_FALLBACK
ps->fallback_used = 0;
#endif
- ps->no_of_user_fds = 0; /* Don't count wakeup pipe and fallback fd */
+ erts_smp_atomic_set(&ps->no_of_user_fds, 0); /* Don't count wakeup pipe and fallback fd */
erts_smp_spin_lock(&pollsets_lock);
ps->next = pollsets;
@@ -2472,7 +2473,7 @@ ERTS_POLL_EXPORT(erts_poll_info)(ErtsPollSet ps, ErtsPollInfo *pip)
pip->memory_size = size;
- pip->poll_set_size = ps->no_of_user_fds;
+ pip->poll_set_size = (int) erts_smp_atomic_read(&ps->no_of_user_fds);
#ifdef ERTS_SMP
pip->poll_set_size++; /* Wakeup pipe */
#endif