From 3eddddcf239c89bbd3c50d1440001a3d384ed40a Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Fri, 16 Sep 2005 19:27:46 -0700 Subject: [PATCH] uml: breakpoint an arbitrary thread This patch implements a stack trace for a thread, not unlike sysrq-t does. The advantage to this is that a break point can be placed on showreqs, so that upon showing the stack, you jump immediately into the debugger. While sysrq-t does the same thing, sysrq-t shows *all* threads stacks. It also doesn't work right now. In the future, I thought it might be acceptable to make this show all pids stacks, but perhaps leaving well enough alone and just using sysrq-t would be okay. For now, upon receiving the stack command, UML switches context to that thread, dumps its registers, and then switches context back to the original thread. Since UML compacts all threads into one of 4 host threads, this sort of mechanism could be expanded in the future to include other debugging helpers that sysrq does not cover. Note by jdike - The main benefit to this is that it brings an arbitrary thread back into context, where it can be examined by gdb. The fact that it dumps it stack is secondary. This provides the capability to examine a sleeping thread, which has existed in tt mode, but not in skas mode until now. Also, the other threads, that sysrq doesn't cover, can be gdb-ed directly anyway. Signed-off-by: Allan Graves Signed-off-by: Jeff Dike Cc: Paolo Giarrusso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/drivers/mconsole_user.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/um/drivers/mconsole_user.c') diff --git a/arch/um/drivers/mconsole_user.c b/arch/um/drivers/mconsole_user.c index fe5afb13252c..a5b8aeade1c5 100644 --- a/arch/um/drivers/mconsole_user.c +++ b/arch/um/drivers/mconsole_user.c @@ -30,6 +30,7 @@ static struct mconsole_command commands[] = { { "go", mconsole_go, MCONSOLE_INTR }, { "log", mconsole_log, MCONSOLE_INTR }, { "proc", mconsole_proc, MCONSOLE_PROC }, + { "stack", mconsole_stack, MCONSOLE_INTR }, }; /* Initialized in mconsole_init, which is an initcall */ -- cgit v1.2.3 From b4fd310e163477236a241580b3b8c29aee65f4cc Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Fri, 16 Sep 2005 19:27:49 -0700 Subject: [PATCH] uml: preserve errno in error paths The poster child for this patch is the third tuntap_user hunk. When an ioctl fails, it properly closes the opened file descriptor and returns. However, the close resets errno to 0, and the 'return errno' that follows returns 0 rather than the value that ioctl set. This caused the caller to believe that the device open succeeded and had opened file descriptor 0, which caused no end of interesting behavior. The rest of this patch is a pass through the UML sources looking for places where errno could be reset before being passed back out. A common culprit is printk, which could call write, being called before errno is returned. In some cases, where the code ends up being much smaller, I just deleted the printk. There was another case where a caller of run_helper looked at errno after a failure, rather than the return value of run_helper, which was the errno value that it wanted. Signed-off-by: Jeff Dike Cc: Paolo Giarrusso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/drivers/mconsole_user.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'arch/um/drivers/mconsole_user.c') diff --git a/arch/um/drivers/mconsole_user.c b/arch/um/drivers/mconsole_user.c index a5b8aeade1c5..310c1f823f26 100644 --- a/arch/um/drivers/mconsole_user.c +++ b/arch/um/drivers/mconsole_user.c @@ -173,9 +173,9 @@ int mconsole_notify(char *sock_name, int type, const void *data, int len) if(notify_sock < 0){ notify_sock = socket(PF_UNIX, SOCK_DGRAM, 0); if(notify_sock < 0){ - printk("mconsole_notify - socket failed, errno = %d\n", - errno); err = -errno; + printk("mconsole_notify - socket failed, errno = %d\n", + err); } } unlock_notify(); @@ -198,8 +198,8 @@ int mconsole_notify(char *sock_name, int type, const void *data, int len) n = sendto(notify_sock, &packet, len, 0, (struct sockaddr *) &target, sizeof(target)); if(n < 0){ - printk("mconsole_notify - sendto failed, errno = %d\n", errno); err = -errno; + printk("mconsole_notify - sendto failed, errno = %d\n", errno); } return(err); } -- cgit v1.2.3