Re: [PATCH] Syslets - Fix cachemiss_thread return value

On Thu, May 31, 2007 at 03:07:16PM -0700, Zach Brown wrote:
> Can you explain what motivated you to send out this patch?
> 
> It used to return 0.  It was changed because, unlike the syslet
> syscalls, sys_io_submit() doesn't have a simple 0 value to indicate
> success.  The current implementation wants to return the number of iocbs
> that were processed, including the one which blocked, from the cachemiss
> thread.  So before calling into an operation it sets task_ret_ret() so
> that the cachemiss thread can return it if it takes over.
> task_ret_reg() is holding a return value that is being returned by the
> cachemiss thread on behalf of a sys_io_submit() which blocked.
> 
> When I made the change I didn't really audit its effect on the other
> paths.  I suppose it's time to do that, and you could help by telling me
> if you saw something bad happen :).

The bad thing was sys_async_exec returning -NOSYS every time a new
cachemiss thread was created.

Without this patch, you'll see sys_async_exec failures with either of
the demos I sent out.  Dunno about the existing ones, but I bet they do
the same.

				Jeff

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Re: [PATCH] Syslets - Fix cachemiss_thread return value

> the demos I sent out.  Dunno about the existing ones, but I bet they do
> the same.

Hmm, they didn't when I ran them, but I'll give yours a try and take a
closer look.  Thanks for taking the time to bring it up.

- z

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[PATCH] syslets demo - fix malloc failure check

Fix the stack malloc failure check.

Signed-off-by: Jeff Dike <jdike <at> linux.intel.com>
--
 syslets/async-test-v5/sys.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-2.6/syslets/async-test-v5/sys.h
===================================================================
--- linux-2.6.orig/syslets/async-test-v5/sys.h	2007-05-31 13:29:57.000000000 -0400
+++ linux-2.6/syslets/async-test-v5/sys.h	2007-06-03 13:12:43.000000000 -0400
 <at>  <at>  -108,9 +108,10  <at>  <at>  static u64 completion_ring[MAX_PENDING];

 static unsigned long thread_stack_alloc()
 {
-	void *stack = malloc(THREAD_STACK_SIZE) + THREAD_STACK_SIZE;
+	void *stack = malloc(THREAD_STACK_SIZE);
 	assert(stack != NULL);

+	stack += THREAD_STACK_SIZE;
 	pr("allocated stack: %p\n", stack);

 	return (unsigned long)stack;

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Re: Query ....

battipatisainagendra Bhavaniprasad wrote:
> I have been beating my head against the wall trying to get a working UML for several days, so any help is
greatly appreciated!I have downloaded
> "linux-2.6.16.tar" (which has UML patch In built) followed by the commands.....
> 
> 
> make defconfig ARCH=um
> 
> make ARCH=um
> 
> but i am getting the following errors...
> 
> arch/um/os-Linux/sys-i386/registers.c: In function 'get_thread_regs':
> 
> arch/um/os-Linux/sys-i386/registers.c:137: error: 'JB_PC' undeclared (first use in this function)
> arch/um/os-Linux/sys-i386/registers.c:137: error: (Each undeclared identifier is reported only once
> arch/um/os-Linux/sys-i386/registers.c:137: error: for each function it appears in.)
> 
> arch/um/os-Linux/sys-i386/registers.c:138: error: 'JB_SP' undeclared (first use in this function)
> arch/um/os-Linux/sys-i386/registers.c:139: error: 'JB_BP' undeclared (first use in this function)
> make[2]: *** [arch/um/os-Linux/sys-i386/registers.o] Error 1
> 
> make[1]: *** [arch/um/os-Linux/sys-i386] Error 2
> 
> Please help me.....
Search the archives, this problem was discussed before and there is a
patch for it.
But the easiest way to fix it is to use something more recent.
Try 2.6.21.3

Error: F_SETLK failed, file already locked by pid 0

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Re: modprobe: Can't locate module scsi_debug

On Tue, May 29, 2007 at 08:37:44PM +0530, rajasekhar.pulluru <at> wipro.com wrote:
> Hi,
> Am a newbie to linux and UML. I have been trying to modprobe the
> scsi_debug,
> [root <at> mandrake82 host]# modprobe scsi_debug
> modprobe: Can't locate module scsi_debug
> 
> Could someone help me to modprobe successfully? 

You build the modules in the UML kernel pool, then copy them into the
UML filesystem - a good way is loop-mounting the UML filesystem and
doing a modules_install with the install directory being /lib in the
loopback mount.

> [root <at> mandrake82 2.4.20-8um]#

You might try something more modern than this - if you have any
trouble with it, no one will be able to help.

				Jeff

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[PATCH 1/2] UML - Fix request->sector update

[ This is post-2.6.22 material - it fixes a bug, but not one that I
think has been seen in the wild, plus an earlier version of this fix
caused file corruption ]

It is theoretically possible for a request to finish and be freed
between writing it to the I/O thread and updating the sector count.
In this case, the update will dereference a freed pointer.

To avoid this, I delay the update until processing the next sg
segment, when the request pointer is known to be good.

Signed-off-by: Jeff Dike <jdike <at> linux.intel.com>
--
 arch/um/drivers/ubd_kern.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Index: linux-2.6.21-mm/arch/um/drivers/ubd_kern.c
===================================================================
--- linux-2.6.21-mm.orig/arch/um/drivers/ubd_kern.c	2007-06-02 12:13:50.000000000 -0400
+++ linux-2.6.21-mm/arch/um/drivers/ubd_kern.c	2007-06-02 22:23:41.000000000 -0400
 <at>  <at>  -1082,7 +1082,7  <at>  <at>  static void do_ubd_request(request_queue
 {
 	struct io_thread_req *io_req;
 	struct request *req;
-	int n;
+	int n, last_sectors;

 	while(1){
 		struct ubd *dev = q->queuedata;
 <at>  <at>  -1098,9 +1098,11  <at>  <at>  static void do_ubd_request(request_queue
 		}

 		req = dev->request;
+		last_sectors = 0;
 		while(dev->start_sg < dev->end_sg){
 			struct scatterlist *sg = &dev->sg[dev->start_sg];

+			req->sector += last_sectors;
 			io_req = kmalloc(sizeof(struct io_thread_req),
 					 GFP_ATOMIC);
 			if(io_req == NULL){
 <at>  <at>  -1112,6 +1114,7  <at>  <at>  static void do_ubd_request(request_queue
 					(unsigned long long) req->sector << 9,
 					sg->offset, sg->length, sg->page);

+			last_sectors = sg->length >> 9;
 			n = os_write_file(thread_fd, &io_req,
 					  sizeof(struct io_thread_req *));
 			if(n != sizeof(struct io_thread_req *)){
 <at>  <at>  -1123,7 +1126,6  <at>  <at>  static void do_ubd_request(request_queue
 				return;
 			}

-			req->sector += sg->length >> 9;
 			dev->start_sg++;
 		}
 		dev->end_sg = 0;

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[PATCH 2/2] UML - Fix kernel stack size on x86_64

[ This is 2.6.22 material ]

Having KERNEL_STACK_ORDER in defconfig overrides the value provided by
Kconfig, breaking UML/x86_64, which wants 2 page stacks.

Signed-off-by: Jeff Dike <jdike <at> linux.intel.com>
--
 arch/um/defconfig |    1 -
 1 file changed, 1 deletion(-)

Index: linux-2.6.21-mm/arch/um/defconfig
===================================================================
--- linux-2.6.21-mm.orig/arch/um/defconfig	2007-06-05 12:18:35.000000000 -0400
+++ linux-2.6.21-mm/arch/um/defconfig	2007-06-05 12:19:12.000000000 -0400
 <at>  <at>  -86,7 +86,6  <at>  <at>  CONFIG_MCONSOLE=y
 # CONFIG_MAGIC_SYSRQ is not set
 CONFIG_NEST_LEVEL=0
 # CONFIG_HIGHMEM is not set
-CONFIG_KERNEL_STACK_ORDER=0
 CONFIG_UML_REAL_TIME_CLOCK=y

 #

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[PATCH] UML - Improve host PTRACE_SYSEMU check

Make the PTRACE_SYSEMU checking more robust.  It will make sure that
system call numbers are reported correctly.  If there is a problem, it
will disable PTRACE_SYSEMU use and use PTRACE_SYSCALL instead.

This fixes a hang on boot on FC6 hosts with a broken PTRACE_SYSEMU.

Signed-off-by: Jeff Dike <jdike <at> linux.intel.com>
--
 arch/um/os-Linux/start_up.c |   24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

Index: linux-2.6.17/arch/um/os-Linux/start_up.c
===================================================================
--- linux-2.6.17.orig/arch/um/os-Linux/start_up.c	2007-06-05 16:53:41.000000000 -0400
+++ linux-2.6.17/arch/um/os-Linux/start_up.c	2007-06-05 16:54:21.000000000 -0400
 <at>  <at>  -144,9 +144,7  <at>  <at>  static int stop_ptraced_child(int pid, v
 		int exit_with = WEXITSTATUS(status);
 		if (exit_with == 2)
 			non_fatal("check_ptrace : child exited with status 2. "
-				  "Serious trouble happening! Try updating "
-				  "your host skas patch!\nDisabling SYSEMU "
-				  "support.");
+				  "\nDisabling SYSEMU support.\n");
 		non_fatal("check_ptrace : child exited with exitcode %d, while "
 			  "expecting %d; status 0x%x\n", exit_with,
 			  exitcode, status);
 <at>  <at>  -209,6 +207,7  <at>  <at>  __uml_setup("nosysemu", nosysemu_cmd_par
 static void __init check_sysemu(void)
 {
 	void *stack;
+	unsigned long regs[MAX_REG_NR];
 	int pid, n, status, count=0;

 	non_fatal("Checking syscall emulation patch for ptrace...");
 <at>  <at>  -225,11 +224,20  <at>  <at>  static void __init check_sysemu(void)
 		fatal("check_sysemu : expected SIGTRAP, got status = %d",
 		      status);

-	n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
-		   os_getpid());
-	if(n < 0)
-		fatal_perror("check_sysemu : failed to modify system call "
-			     "return");
+	if(ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
+		fatal_perror("check_sysemu : PTRACE_GETREGS failed");
+	if(PT_SYSCALL_NR(regs) != __NR_getpid){
+		non_fatal("check_sysemu got system call number %d, "
+			  "expected %d...", PT_SYSCALL_NR(regs), __NR_getpid);
+		goto fail;
+	}
+
+	n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET, os_getpid());
+	if(n < 0){
+		non_fatal("check_sysemu : failed to modify system call "
+			  "return");
+		goto fail;
+	}

 	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
 		goto fail_stopped;

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Re: [PATCH 2/2] UML - Fix kernel stack size on x86_64

On Tue, 5 Jun 2007 16:50:55 -0400
Jeff Dike <jdike <at> addtoit.com> wrote:

> [ This is 2.6.22 material ]
> 
> Having KERNEL_STACK_ORDER in defconfig overrides the value provided by
> Kconfig, breaking UML/x86_64, which wants 2 page stacks.
> 
> Signed-off-by: Jeff Dike <jdike <at> linux.intel.com>
> --
>  arch/um/defconfig |    1 -
>  1 file changed, 1 deletion(-)
> 
> Index: linux-2.6.21-mm/arch/um/defconfig
> ===================================================================
> --- linux-2.6.21-mm.orig/arch/um/defconfig	2007-06-05 12:18:35.000000000 -0400
> +++ linux-2.6.21-mm/arch/um/defconfig	2007-06-05 12:19:12.000000000 -0400
>  <at>  <at>  -86,7 +86,6  <at>  <at>  CONFIG_MCONSOLE=y
>  # CONFIG_MAGIC_SYSRQ is not set
>  CONFIG_NEST_LEVEL=0
>  # CONFIG_HIGHMEM is not set
> -CONFIG_KERNEL_STACK_ORDER=0
>  CONFIG_UML_REAL_TIME_CLOCK=y
>  

That means the Kconfig rules are wrong, surely?