From: Paolo 'Blaisorblade' Giarrusso Date: Fri, 31 Mar 2006 10:30:21 +0000 (-0800) Subject: [PATCH] uml: clean arch_switch usage X-Git-Tag: v2.6.17-rc1~107 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=972410b0232e97609fcefc8e408fe3037fcd607b;p=platform%2Fkernel%2Flinux-3.10.git [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 Acked-by: Jeff Dike Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/um/include/kern_util.h b/arch/um/include/kern_util.h index 07176d9..4255713 100644 --- a/arch/um/include/kern_util.h +++ b/arch/um/include/kern_util.h @@ -116,7 +116,11 @@ extern void *get_current(void); extern struct task_struct *get_task(int pid, int require); extern void machine_halt(void); extern int is_syscall(unsigned long addr); -extern void arch_switch(void); + +extern void arch_switch_to_tt(struct task_struct *from, struct task_struct *to); + +extern void arch_switch_to_skas(struct task_struct *from, struct task_struct *to); + extern void free_irq(unsigned int, void *); extern int cpu(void); diff --git a/arch/um/include/sysdep-i386/ptrace.h b/arch/um/include/sysdep-i386/ptrace.h index c8ee955..6670cc9 100644 --- a/arch/um/include/sysdep-i386/ptrace.h +++ b/arch/um/include/sysdep-i386/ptrace.h @@ -14,7 +14,12 @@ #define MAX_REG_NR (UM_FRAME_SIZE / sizeof(unsigned long)) #define MAX_REG_OFFSET (UM_FRAME_SIZE) +#ifdef UML_CONFIG_PT_PROXY extern void update_debugregs(int seq); +#else +static inline void update_debugregs(int seq) {} +#endif + /* syscall emulation path in ptrace */ diff --git a/arch/um/kernel/skas/process_kern.c b/arch/um/kernel/skas/process_kern.c index 3f70a2e..14360ac 100644 --- a/arch/um/kernel/skas/process_kern.c +++ b/arch/um/kernel/skas/process_kern.c @@ -35,6 +35,8 @@ void switch_to_skas(void *prev, void *next) switch_threads(&from->thread.mode.skas.switch_buf, to->thread.mode.skas.switch_buf); + arch_switch_to_skas(current->thread.prev_sched, current); + if(current->pid == 0) switch_timers(1); } diff --git a/arch/um/kernel/tt/process_kern.c b/arch/um/kernel/tt/process_kern.c index 295c1ac..a9c1443 100644 --- a/arch/um/kernel/tt/process_kern.c +++ b/arch/um/kernel/tt/process_kern.c @@ -51,6 +51,13 @@ void switch_to_tt(void *prev, void *next) c = 0; + /* Notice that here we "up" the semaphore on which "to" is waiting, and + * below (the read) we wait on this semaphore (which is implemented by + * switch_pipe) and go sleeping. Thus, after that, we have resumed in + * "to", and can't use any more the value of "from" (which is outdated), + * nor the value in "to" (since it was the task which stole us the CPU, + * which we don't care about). */ + err = os_write_file(to->thread.mode.tt.switch_pipe[1], &c, sizeof(c)); if(err != sizeof(c)) panic("write of switch_pipe failed, err = %d", -err); @@ -77,7 +84,7 @@ void switch_to_tt(void *prev, void *next) change_sig(SIGALRM, alrm); change_sig(SIGPROF, prof); - arch_switch(); + arch_switch_to_tt(prev_sched, current); flush_tlb_all(); local_irq_restore(flags); @@ -141,7 +148,6 @@ static void new_thread_handler(int sig) set_cmdline("(kernel thread)"); change_sig(SIGUSR1, 1); - change_sig(SIGVTALRM, 1); change_sig(SIGPROF, 1); local_irq_enable(); if(!run_kernel_thread(fn, arg, ¤t->thread.exec_buf)) diff --git a/arch/um/sys-i386/ptrace.c b/arch/um/sys-i386/ptrace.c index ff94ede..927fcd9 100644 --- a/arch/um/sys-i386/ptrace.c +++ b/arch/um/sys-i386/ptrace.c @@ -15,9 +15,13 @@ #include "sysdep/sigcontext.h" #include "sysdep/sc.h" -void arch_switch(void) +void arch_switch_to_tt(struct task_struct *from, struct task_struct *to) +{ + update_debugregs(to->thread.arch.debugregs_seq); +} + +void arch_switch_to_skas(struct task_struct *from, struct task_struct *to) { - update_debugregs(current->thread.arch.debugregs_seq); } int is_syscall(unsigned long addr) 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 @@ int ptrace_setfpregs(long pid, unsigned long *regs) 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 @@ static void read_debugregs(int pid, unsigned long *regs) /* 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 @@ void arch_leave_kernel(void *task, int pid) 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 @@ static void update_debugregs_cb(void *arg) write_debugregs(pid, kernel_debugregs); } +/* Optimized out in its header when not defined */ void update_debugregs(int seq) { int me; @@ -118,6 +125,7 @@ void update_debugregs(int seq) me = os_getpid(); initial_thread_cb(update_debugregs_cb, &me); } +#endif /* * Overrides for Emacs so that we follow Linus's tabbing style.