From 18879fef1741464e522624bcc529048400453e0d Mon Sep 17 00:00:00 2001 From: Yao Qi Date: Tue, 26 Jan 2016 13:50:22 +0000 Subject: [PATCH] [GDBserver] Check input interrupt after reading in a packet GDBserver may read some packet together with '\003' in one go. We've already checked '\003' first when reading packet by my patch, Check input interrupt first when reading packet https://sourceware.org/ml/gdb-patches/2016-01/msg00057.html but if we don't check '\003' *after* each packet, the interrupt will be processed next time GDBserver reads from the buffer, so that the interrupt isn't processed in time. For example, GDB sends vCont;c and interrupt (see gdb.base/interrupt-noterm.exp), we'll resume the inferior and wait once packet vCont;c is seen. If we don't check the interrupt character after vCont;c packet, interrupt character will stay in the buffer unattended until GDBserver returns from the wait, which may take a while. Note that since we've read '\003' from file descriptor, SIGIO signal handler input_interrupt doesn't help either. This issue can be exposed by hacking the end of getpkt like @@ -1041,6 +1050,9 @@ getpkt (char *buf) } } + if (readchar_bufcnt > 0) + gdb_assert (*readchar_bufp != '\003'); + return bp - buf; } and this can trigger internal error, (gdb) PASS: gdb.base/interrupt-noterm.exp: interrupt Remote connection closed^M (gdb) FAIL: gdb.base/interrupt-noterm.exp: inferior received SIGINT Remote debugging from host 10.2.206.40^M /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/remote-utils.c:1054: A problem internal to GDBserver has been detected.^M getpkt: Assertion `*readchar_bufp != '\003'' failed.^M This patch is to peek the buffer, if it is '\003', consume it and call *the_target->request_interrupt. gdb/gdbserver: 2016-01-26 Yao Qi * remote-utils.c (getpkt): If the buffer isn't empty, and the first character is '\003', call *the_target->request_interrupt. --- gdb/gdbserver/ChangeLog | 5 +++++ gdb/gdbserver/remote-utils.c | 16 ++++++++++++++++ 2 files changed, 21 insertions(+) diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog index 2e94aa88bf..4aa7350db3 100644 --- a/gdb/gdbserver/ChangeLog +++ b/gdb/gdbserver/ChangeLog @@ -1,3 +1,8 @@ +2016-01-26 Yao Qi + + * remote-utils.c (getpkt): If the buffer isn't empty, and the + first character is '\003', call *the_target->request_interrupt. + 2016-01-25 Yao Qi * remote-utils.c (new_thread_notify): Remove. diff --git a/gdb/gdbserver/remote-utils.c b/gdb/gdbserver/remote-utils.c index 292197a4c9..ccc99f16a2 100644 --- a/gdb/gdbserver/remote-utils.c +++ b/gdb/gdbserver/remote-utils.c @@ -1041,6 +1041,22 @@ getpkt (char *buf) } } + /* The readchar above may have already read a '\003' out of the socket + and moved it to the local buffer. For example, when GDB sends + vCont;c immediately followed by interrupt (see + gdb.base/interrupt-noterm.exp). As soon as we see the vCont;c, we'll + resume the inferior and wait. Since we've already moved the '\003' + to the local buffer, SIGIO won't help. In that case, if we don't + check for interrupt after the vCont;c packet, the interrupt character + would stay in the buffer unattended until after the next (unrelated) + stop. */ + while (readchar_bufcnt > 0 && *readchar_bufp == '\003') + { + /* Consume the interrupt character in the buffer. */ + readchar (); + (*the_target->request_interrupt) (); + } + return bp - buf; } -- 2.34.1