[PATCH 18/30] Fix inconsistent handling of EINTR in ser-*.c backends

Pedro Alves
2016-03-18T19:18:56Z

- If serial->write_prim returns EINTR, ser_bas_write returns it to the
caller. This just looks wrong to me -- part of the output may have
already been sent, and there's no way for the caller to know that,
and thus no way for a caller to handle a partial write correctly.

- While ser-unix.c:ser_unix_read_prim retries on EINTR,
ser-tcp.c:net_read_prim does not.

This commit moves EINTR handling to the ser_base_write and
ser_base_readchar level, so all serial backends (at least those that
use it) end up handling EINTR consistently.

gdb/ChangeLog:
yyyy-mm-dd Pedro Alves <palves@redhat.com>

* ser-base.c (fd_event): Retry read_prim on EINTR.
(do_ser_base_readchar): Retry read_prim on EINTR.
(ser_base_write): Retry write_prim on EINTR.
* ser-unix.c (ser_unix_read_prim): Don't retry on EINTR here.
(ser_unix_write_prim): Remove comment.
---
gdb/ser-base.c | 20 +++++++++++++++++---
gdb/ser-unix.c | 12 +-----------
2 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/gdb/ser-base.c b/gdb/ser-base.c
index 21d52cd..25af66a 100644
--- a/gdb/ser-base.c
+++ b/gdb/ser-base.c
@@ -164,7 +164,13 @@ fd_event (int error, void *context)
pull characters out of the buffer. See also
generic_readchar(). */
int nr;
- nr = scb->ops->read_prim (scb, BUFSIZ);
+
+ do
+ {
+ nr = scb->ops->read_prim (scb, BUFSIZ);
+ }
+ while (nr < 0 && errno == EINTR);
+
if (nr == 0)
{
scb->bufcnt = SERIAL_EOF;
@@ -358,7 +364,11 @@ do_ser_base_readchar (struct serial *scb, int timeout)
if (status < 0)
return status;

- status = scb->ops->read_prim (scb, BUFSIZ);
+ do
+ {
+ status = scb->ops->read_prim (scb, BUFSIZ);
+ }
+ while (status < 0 && errno == EINTR);

if (status <= 0)
{
@@ -448,7 +458,11 @@ ser_base_write (struct serial *scb, const void *buf, size_t count)
cc = scb->ops->write_prim (scb, str, count);

if (cc < 0)
- return 1;
+ {
+ if (errno == EINTR)
+ continue;
+ return 1;
+ }
count -= cc;
str += cc;
}
diff --git a/gdb/ser-unix.c b/gdb/ser-unix.c
index c54b2e1..562e98b 100644
--- a/gdb/ser-unix.c
+++ b/gdb/ser-unix.c
@@ -1002,21 +1002,11 @@ when debugging using remote targets."),
int
ser_unix_read_prim (struct serial *scb, size_t count)
{
- int status;
-
- while (1)
- {
- status = read (scb->fd, scb->buf, count);
- if (status != -1 || errno != EINTR)
- break;
- }
- return status;
+ return read (scb->fd, scb->buf, count);
}

int
ser_unix_write_prim (struct serial *scb, const void *buf, size_t len)
{
- /* ??? Historically, GDB has not retried calls to "write" that
- result in EINTR. */
return write (scb->fd, buf, len);
}
--
2.5.0