[PATCH] uml: clean arch_switch usage
Call arch_switch also in switch_to_skas, even if it's, for now, a no-op for
that case (and mark this in the comment); this will change soon.
Also, arch_switch for TT mode is actually useless when the PT proxy (a
complicate debugging instrumentation for TT mode) is not enabled. In fact, it
only calls update_debugregs, which checks debugregs_seq against seq (to check
if the registers are up-to-date - seq here means a "version number" of the
registers).
If the ptrace proxy is not enabled, debugregs_seq always stays 0 and
update_debugregs will be a no-op. So, optimize this out (the compiler can't
do it).
Also, I've been disappointed by the fact that it would make a lot of sense if,
after calling a successful
update_debugregs(current->thread.arch.debugregs_seq),
current->thread.arch.debugregs_seq were updated with the new debugregs_seq.
But this is not done. Is this a bug or a feature? For all purposes, it seems
a bug (otherwise the whole mechanism does not make sense, which is also a
possibility to check), which causes some performance only problems (not
correctness), since we write_debugregs when not needed.
Also, as suggested by Jeff, remove a redundant enabling of SIGVTALRM,
comprised in the subsequent local_irq_enable(). I'm just a bit dubious if
ordering matters there...
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Acked-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/um/sys-i386/ptrace_user.c b/arch/um/sys-i386/ptrace_user.c
index 7c376c9..9f3bd8e 100644
--- a/arch/um/sys-i386/ptrace_user.c
+++ b/arch/um/sys-i386/ptrace_user.c
@@ -14,6 +14,7 @@
#include "sysdep/thread.h"
#include "user.h"
#include "os.h"
+#include "uml-config.h"
int ptrace_getregs(long pid, unsigned long *regs_out)
{
@@ -43,6 +44,7 @@
return 0;
}
+/* All the below stuff is of interest for TT mode only */
static void write_debugregs(int pid, unsigned long *regs)
{
struct user *dummy;
@@ -75,7 +77,6 @@
/* Accessed only by the tracing thread */
static unsigned long kernel_debugregs[8] = { [ 0 ... 7 ] = 0 };
-static int debugregs_seq = 0;
void arch_enter_kernel(void *task, int pid)
{
@@ -89,6 +90,11 @@
write_debugregs(pid, TASK_DEBUGREGS(task));
}
+#ifdef UML_CONFIG_PT_PROXY
+/* Accessed only by the tracing thread */
+static int debugregs_seq;
+
+/* Only called by the ptrace proxy */
void ptrace_pokeuser(unsigned long addr, unsigned long data)
{
if((addr < offsetof(struct user, u_debugreg[0])) ||
@@ -109,6 +115,7 @@
write_debugregs(pid, kernel_debugregs);
}
+/* Optimized out in its header when not defined */
void update_debugregs(int seq)
{
int me;
@@ -118,6 +125,7 @@
me = os_getpid();
initial_thread_cb(update_debugregs_cb, &me);
}
+#endif
/*
* Overrides for Emacs so that we follow Linus's tabbing style.