[PATCH 2/4] tile: support CONTEXT_TRACKING and thus NOHZ_FULL

From: cmetcalf
Date: Tue Mar 24 2015 - 15:22:46 EST

From: Chris Metcalf <cmetcalf@xxxxxxxxxx>

Add the TIF_NOHZ flag appropriately.

Add call to user_exit() on entry to do_work_pending() and on entry
to syscalls via do_syscall_trace_enter(), and also the top of
do_syscall_trace_exit() just because it's done in x86.

Add call to user_enter() at the bottom of do_work_pending() once we
have no more work to do before returning to userspace.

Wrap all the trap code in exception_enter() / exception_exit().

Signed-off-by: Chris Metcalf <cmetcalf@xxxxxxxxxx>
---
arch/tile/Kconfig | 1 +
arch/tile/include/asm/thread_info.h | 9 ++++++---
arch/tile/kernel/process.c | 12 ++++++++----
arch/tile/kernel/ptrace.c | 22 ++++++++++++++++++++--
arch/tile/kernel/single_step.c | 3 +++
arch/tile/kernel/traps.c | 16 +++++++++-------
arch/tile/kernel/unaligned.c | 22 +++++++++++++---------
arch/tile/mm/fault.c | 10 +++++++---
8 files changed, 67 insertions(+), 28 deletions(-)

diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig
index 7cca41842a9e..c3a31f8bb09c 100644
--- a/arch/tile/Kconfig
+++ b/arch/tile/Kconfig
@@ -27,6 +27,7 @@ config TILE
select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
select HAVE_DEBUG_STACKOVERFLOW
select ARCH_WANT_FRAME_POINTERS
+ select HAVE_CONTEXT_TRACKING

# FIXME: investigate whether we need/want these options.
# select HAVE_IOREMAP_PROT
diff --git a/arch/tile/include/asm/thread_info.h b/arch/tile/include/asm/thread_info.h
index 96c14c1430d8..6130a3db505b 100644
--- a/arch/tile/include/asm/thread_info.h
+++ b/arch/tile/include/asm/thread_info.h
@@ -126,6 +126,7 @@ extern void _cpu_idle(void);
#define TIF_NOTIFY_RESUME 8 /* callback before returning to user */
#define TIF_SYSCALL_TRACEPOINT 9 /* syscall tracepoint instrumentation */
#define TIF_POLLING_NRFLAG 10 /* idle is polling for TIF_NEED_RESCHED */
+#define TIF_NOHZ 11 /* in adaptive nohz mode */

#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
@@ -138,14 +139,16 @@ extern void _cpu_idle(void);
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
#define _TIF_SYSCALL_TRACEPOINT (1<<TIF_SYSCALL_TRACEPOINT)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
+#define _TIF_NOHZ (1<<TIF_NOHZ)

/* Work to do on any return to user space. */
#define _TIF_ALLWORK_MASK \
- (_TIF_SIGPENDING|_TIF_NEED_RESCHED|_TIF_SINGLESTEP|\
- _TIF_ASYNC_TLB|_TIF_NOTIFY_RESUME)
+ (_TIF_SIGPENDING | _TIF_NEED_RESCHED | _TIF_SINGLESTEP | \
+ _TIF_ASYNC_TLB | _TIF_NOTIFY_RESUME | _TIF_NOHZ)

/* Work to do at syscall entry. */
-#define _TIF_SYSCALL_ENTRY_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT)
+#define _TIF_SYSCALL_ENTRY_WORK \
+ (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT | _TIF_NOHZ)

/* Work to do at syscall exit. */
#define _TIF_SYSCALL_EXIT_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT)
diff --git a/arch/tile/kernel/process.c b/arch/tile/kernel/process.c
index 48e5773dd0b7..b403c2e3e263 100644
--- a/arch/tile/kernel/process.c
+++ b/arch/tile/kernel/process.c
@@ -27,6 +27,7 @@
#include <linux/kernel.h>
#include <linux/tracehook.h>
#include <linux/signal.h>
+#include <linux/context_tracking.h>
#include <asm/stack.h>
#include <asm/switch_to.h>
#include <asm/homecache.h>
@@ -474,6 +475,8 @@ int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
if (!user_mode(regs))
return 0;

+ user_exit();
+
/* Enable interrupts; they are disabled again on return to caller. */
local_irq_enable();

@@ -496,11 +499,12 @@ int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
tracehook_notify_resume(regs);
return 1;
}
- if (thread_info_flags & _TIF_SINGLESTEP) {
+ if (thread_info_flags & _TIF_SINGLESTEP)
single_step_once(regs);
- return 0;
- }
- panic("work_pending: bad flags %#x\n", thread_info_flags);
+
+ user_enter();
+
+ return 0;
}

unsigned long get_wchan(struct task_struct *p)
diff --git a/arch/tile/kernel/ptrace.c b/arch/tile/kernel/ptrace.c
index de98c6ddf136..f84eed8243da 100644
--- a/arch/tile/kernel/ptrace.c
+++ b/arch/tile/kernel/ptrace.c
@@ -22,6 +22,7 @@
#include <linux/regset.h>
#include <linux/elf.h>
#include <linux/tracehook.h>
+#include <linux/context_tracking.h>
#include <asm/traps.h>
#include <arch/chip.h>

@@ -252,12 +253,21 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,

int do_syscall_trace_enter(struct pt_regs *regs)
{
- if (test_thread_flag(TIF_SYSCALL_TRACE)) {
+ u32 work = ACCESS_ONCE(current_thread_info()->flags);
+
+ /*
+ * If TIF_NOHZ is set, we are required to call user_exit() before
+ * doing anything that could touch RCU.
+ */
+ if (work & _TIF_NOHZ)
+ user_exit();
+
+ if (work & _TIF_SYSCALL_TRACE) {
if (tracehook_report_syscall_entry(regs))
regs->regs[TREG_SYSCALL_NR] = -1;
}

- if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
+ if (work & _TIF_SYSCALL_TRACEPOINT)
trace_sys_enter(regs, regs->regs[TREG_SYSCALL_NR]);

return regs->regs[TREG_SYSCALL_NR];
@@ -268,6 +278,12 @@ void do_syscall_trace_exit(struct pt_regs *regs)
long errno;

/*
+ * We may come here right after calling schedule_user()
+ * in which case we can be in RCU user mode.
+ */
+ user_exit();
+
+ /*
* The standard tile calling convention returns the value (or negative
* errno) in r0, and zero (or positive errno) in r1.
* It saves a couple of cycles on the hot path to do this work in
@@ -303,5 +319,7 @@ void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs)
/* Handle synthetic interrupt delivered only by the simulator. */
void __kprobes do_breakpoint(struct pt_regs* regs, int fault_num)
{
+ enum ctx_state prev_state = exception_enter();
send_sigtrap(current, regs);
+ exception_exit(prev_state);
}
diff --git a/arch/tile/kernel/single_step.c b/arch/tile/kernel/single_step.c
index 862973074bf9..53f7b9def07b 100644
--- a/arch/tile/kernel/single_step.c
+++ b/arch/tile/kernel/single_step.c
@@ -23,6 +23,7 @@
#include <linux/types.h>
#include <linux/err.h>
#include <linux/prctl.h>
+#include <linux/context_tracking.h>
#include <asm/cacheflush.h>
#include <asm/traps.h>
#include <asm/uaccess.h>
@@ -738,6 +739,7 @@ static DEFINE_PER_CPU(unsigned long, ss_saved_pc);

void gx_singlestep_handle(struct pt_regs *regs, int fault_num)
{
+ enum ctx_state prev_state = exception_enter();
unsigned long *ss_pc = this_cpu_ptr(&ss_saved_pc);
struct thread_info *info = (void *)current_thread_info();
int is_single_step = test_ti_thread_flag(info, TIF_SINGLESTEP);
@@ -754,6 +756,7 @@ void gx_singlestep_handle(struct pt_regs *regs, int fault_num)
__insn_mtspr(SPR_SINGLE_STEP_CONTROL_K, control);
send_sigtrap(current, regs);
}
+ exception_exit(prev_state);
}


diff --git a/arch/tile/kernel/traps.c b/arch/tile/kernel/traps.c
index bf841ca517bb..312fc134c1cb 100644
--- a/arch/tile/kernel/traps.c
+++ b/arch/tile/kernel/traps.c
@@ -20,6 +20,7 @@
#include <linux/reboot.h>
#include <linux/uaccess.h>
#include <linux/ptrace.h>
+#include <linux/context_tracking.h>
#include <asm/stack.h>
#include <asm/traps.h>
#include <asm/setup.h>
@@ -253,6 +254,7 @@ static int do_bpt(struct pt_regs *regs)
void __kprobes do_trap(struct pt_regs *regs, int fault_num,
unsigned long reason)
{
+ enum ctx_state prev_state = exception_enter();
siginfo_t info = { 0 };
int signo, code;
unsigned long address = 0;
@@ -261,7 +263,7 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,

/* Handle breakpoints, etc. */
if (is_kernel && fault_num == INT_ILL && do_bpt(regs))
- return;
+ goto done;

/* Re-enable interrupts, if they were previously enabled. */
if (!(regs->flags & PT_FLAGS_DISABLE_IRQ))
@@ -275,7 +277,7 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
const char *name;
char buf[100];
if (fixup_exception(regs)) /* ILL_TRANS or UNALIGN_DATA */
- return;
+ goto done;
if (fault_num >= 0 &&
fault_num < ARRAY_SIZE(int_name) &&
int_name[fault_num] != NULL)
@@ -294,7 +296,6 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
fault_num, name, regs->pc, buf);
show_regs(regs);
do_exit(SIGKILL); /* FIXME: implement i386 die() */
- return;
}

switch (fault_num) {
@@ -308,7 +309,6 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
pr_err("Unreadable instruction for INT_ILL: %#lx\n",
regs->pc);
do_exit(SIGKILL);
- return;
}
if (!special_ill(instr, &signo, &code)) {
signo = SIGILL;
@@ -319,7 +319,7 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
case INT_GPV:
#if CHIP_HAS_TILE_DMA()
if (retry_gpv(reason))
- return;
+ goto done;
#endif
/*FALLTHROUGH*/
case INT_UDN_ACCESS:
@@ -346,7 +346,7 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
if (!state ||
(void __user *)(regs->pc) != state->buffer) {
single_step_once(regs);
- return;
+ goto done;
}
}
#endif
@@ -380,7 +380,6 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
#endif
default:
panic("Unexpected do_trap interrupt number %d", fault_num);
- return;
}

info.si_signo = signo;
@@ -391,6 +390,9 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
if (signo != SIGTRAP)
trace_unhandled_signal("trap", regs, address, signo);
force_sig_info(signo, &info, current);
+
+done:
+ exception_exit(prev_state);
}

void kernel_double_fault(int dummy, ulong pc, ulong lr, ulong sp, ulong r52)
diff --git a/arch/tile/kernel/unaligned.c b/arch/tile/kernel/unaligned.c
index 7d9a83be0aca..d075f92ccee0 100644
--- a/arch/tile/kernel/unaligned.c
+++ b/arch/tile/kernel/unaligned.c
@@ -25,6 +25,7 @@
#include <linux/module.h>
#include <linux/compat.h>
#include <linux/prctl.h>
+#include <linux/context_tracking.h>
#include <asm/cacheflush.h>
#include <asm/traps.h>
#include <asm/uaccess.h>
@@ -1448,6 +1449,7 @@ void jit_bundle_gen(struct pt_regs *regs, tilegx_bundle_bits bundle,

void do_unaligned(struct pt_regs *regs, int vecnum)
{
+ enum ctx_state prev_state = exception_enter();
tilegx_bundle_bits __user *pc;
tilegx_bundle_bits bundle;
struct thread_info *info = current_thread_info();
@@ -1487,12 +1489,11 @@ void do_unaligned(struct pt_regs *regs, int vecnum)
(int)unaligned_fixup,
(unsigned long long)regs->ex1,
(unsigned long long)regs->pc);
- return;
+ } else {
+ /* Not fixable. Go panic. */
+ panic("Unalign exception in Kernel. pc=%lx",
+ regs->pc);
}
- /* Not fixable. Go panic. */
- panic("Unalign exception in Kernel. pc=%lx",
- regs->pc);
- return;
} else {
/*
* Try to fix the exception. If we can't, panic the
@@ -1501,8 +1502,8 @@ void do_unaligned(struct pt_regs *regs, int vecnum)
bundle = GX_INSN_BSWAP(
*((tilegx_bundle_bits *)(regs->pc)));
jit_bundle_gen(regs, bundle, align_ctl);
- return;
}
+ goto done;
}

/*
@@ -1526,7 +1527,7 @@ void do_unaligned(struct pt_regs *regs, int vecnum)

trace_unhandled_signal("unaligned fixup trap", regs, 0, SIGBUS);
force_sig_info(info.si_signo, &info, current);
- return;
+ goto done;
}


@@ -1543,7 +1544,7 @@ void do_unaligned(struct pt_regs *regs, int vecnum)
trace_unhandled_signal("segfault in unalign fixup", regs,
(unsigned long)info.si_addr, SIGSEGV);
force_sig_info(info.si_signo, &info, current);
- return;
+ goto done;
}

if (!info->unalign_jit_base) {
@@ -1578,7 +1579,7 @@ void do_unaligned(struct pt_regs *regs, int vecnum)

if (IS_ERR((void __force *)user_page)) {
pr_err("Out of kernel pages trying do_mmap\n");
- return;
+ goto done;
}

/* Save the address in the thread_info struct */
@@ -1591,6 +1592,9 @@ void do_unaligned(struct pt_regs *regs, int vecnum)

/* Generate unalign JIT */
jit_bundle_gen(regs, GX_INSN_BSWAP(bundle), align_ctl);
+
+done:
+ exception_exit(prev_state);
}

#endif /* __tilegx__ */
diff --git a/arch/tile/mm/fault.c b/arch/tile/mm/fault.c
index 0f61a73534e6..e83cc999da02 100644
--- a/arch/tile/mm/fault.c
+++ b/arch/tile/mm/fault.c
@@ -35,6 +35,7 @@
#include <linux/syscalls.h>
#include <linux/uaccess.h>
#include <linux/kdebug.h>
+#include <linux/context_tracking.h>

#include <asm/pgalloc.h>
#include <asm/sections.h>
@@ -702,6 +703,7 @@ void do_page_fault(struct pt_regs *regs, int fault_num,
unsigned long address, unsigned long write)
{
int is_page_fault;
+ enum ctx_state prev_state = exception_enter();

#ifdef CONFIG_KPROBES
/*
@@ -711,7 +713,7 @@ void do_page_fault(struct pt_regs *regs, int fault_num,
*/
if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
regs->faultnum, SIGSEGV) == NOTIFY_STOP)
- return;
+ goto done;
#endif

#ifdef __tilegx__
@@ -750,7 +752,6 @@ void do_page_fault(struct pt_regs *regs, int fault_num,
current->comm, current->pid, pc, address);
show_regs(regs);
do_group_exit(SIGKILL);
- return;
}
}
#else
@@ -834,12 +835,15 @@ void do_page_fault(struct pt_regs *regs, int fault_num,
async->is_fault = is_page_fault;
async->is_write = write;
async->address = address;
- return;
+ goto done;
}
}
#endif

handle_page_fault(regs, fault_num, is_page_fault, address, write);
+
+done:
+ exception_exit(prev_state);
}


--
2.1.2

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