Tony-san,
How about this patch as a draft?
This patch does:
- enable interrupts before calling schedule() as same as others, ex. x86
- enable interrupts during ia64_do_signal() and ia64_sync_krbs()
- do_notify_resume_user() is still called with interrupts disabled, since
we can take short path of fsys_mode if-statement quickly.
- pfm_handle_work() is also called with interrupts disabled, since
it can deal interrupt mask within itself.
- fix/add some comments/notes
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@xxxxxxxxxxxxxx>
---
arch/ia64/kernel/entry.S | 26 ++++++++++++++++----------
arch/ia64/kernel/perfmon.c | 16 ++++++++++------
arch/ia64/kernel/process.c | 25 +++++++++++++++++++++----
3 files changed, 47 insertions(+), 20 deletions(-)
diff --git a/arch/ia64/kernel/entry.S b/arch/ia64/kernel/entry.S
index e49ad8c..ca2bb95 100644
--- a/arch/ia64/kernel/entry.S
+++ b/arch/ia64/kernel/entry.S
@@ -1156,6 +1156,9 @@ skip_rbs_switch:
* r31 = current->thread_info->flags
* On exit:
* p6 = TRUE if work-pending-check needs to be redone
+ *
+ * Interrupts are disabled on entry, reenabled depend on work, and
+ * disabled on exit.
*/
.work_pending_syscall:
add r2=-8,r2
@@ -1164,16 +1167,16 @@ skip_rbs_switch:
st8 [r2]=r8
st8 [r3]=r10
.work_pending:
- tbit.z p6,p0=r31,TIF_NEED_RESCHED // current_thread_info()->need_resched==0?
+ tbit.z p6,p0=r31,TIF_NEED_RESCHED // is resched not needed?
(p6) br.cond.sptk.few .notify
#ifdef CONFIG_PREEMPT
(pKStk) dep r21=-1,r0,PREEMPT_ACTIVE_BIT,1
;;
(pKStk) st4 [r20]=r21
- ssm psr.i // enable interrupts
#endif
+ ssm psr.i // enable interrupts
br.call.spnt.many rp=schedule
-.ret9: cmp.eq p6,p0=r0,r0 // p6 <- 1
+.ret9: cmp.eq p6,p0=r0,r0 // p6 <- 1 (re-check)
rsm psr.i // disable interrupts
;;
#ifdef CONFIG_PREEMPT
@@ -1182,13 +1185,13 @@ skip_rbs_switch:
(pKStk) st4 [r20]=r0 // preempt_count() <- 0
#endif
(pLvSys)br.cond.sptk.few .work_pending_syscall_end
- br.cond.sptk.many .work_processed_kernel // re-check
+ br.cond.sptk.many .work_processed_kernel
.notify:
(pUStk) br.call.spnt.many rp=notify_resume_user
-.ret10: cmp.ne p6,p0=r0,r0 // p6 <- 0
+.ret10: cmp.ne p6,p0=r0,r0 // p6 <- 0 (don't re-check)
(pLvSys)br.cond.sptk.few .work_pending_syscall_end
- br.cond.sptk.many .work_processed_kernel // don't re-check
+ br.cond.sptk.many .work_processed_kernel
.work_pending_syscall_end:
adds r2=PT(R8)+16,r12
@@ -1196,7 +1199,7 @@ skip_rbs_switch:
;;
ld8 r8=[r2]
ld8 r10=[r3]
- br.cond.sptk.many .work_processed_syscall // re-check
+ br.cond.sptk.many .work_processed_syscall
END(ia64_leave_kernel)
@@ -1234,9 +1237,12 @@ GLOBAL_ENTRY(ia64_invoke_schedule_tail)
END(ia64_invoke_schedule_tail)
/*
- * Setup stack and call do_notify_resume_user(). Note that pSys and pNonSys need to
- * be set up by the caller. We declare 8 input registers so the system call
- * args get preserved, in case we need to restart a system call.
+ * Setup stack and call do_notify_resume_user(), keeping interrupts
+ * disabled.
+ *
+ * Note that pSys and pNonSys need to be set up by the caller.
+ * We declare 8 input registers so the system call args get preserved,
+ * in case we need to restart a system call.
*/
ENTRY(notify_resume_user)
.prologue ASM_UNW_PRLG_RP|ASM_UNW_PRLG_PFS, ASM_UNW_PRLG_GRSAVE(8)
diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index c1ad27d..71d0513 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -5013,12 +5013,13 @@ pfm_context_force_terminate(pfm_context_t *ctx, struct pt_regs *regs)
}
static int pfm_ovfl_notify_user(pfm_context_t *ctx, unsigned long ovfl_pmds);
+
/*
* pfm_handle_work() can be called with interrupts enabled
* (TIF_NEED_RESCHED) or disabled. The down_interruptible
* call may sleep, therefore we must re-enable interrupts
* to avoid deadlocks. It is safe to do so because this function
- * is called ONLY when returning to user level (PUStk=1), in which case
+ * is called ONLY when returning to user level (pUStk=1), in which case
* there is no risk of kernel stack overflow due to deep
* interrupt nesting.
*/
@@ -5034,7 +5035,8 @@ pfm_handle_work(void)
ctx = PFM_GET_CTX(current);
if (ctx == NULL) {
- printk(KERN_ERR "perfmon: [%d] has no PFM context\n", task_pid_nr(current));
+ printk(KERN_ERR "perfmon: [%d] has no PFM context\n",
+ task_pid_nr(current));
return;
}
@@ -5058,11 +5060,12 @@ pfm_handle_work(void)
/*
* must be done before we check for simple-reset mode
*/
- if (ctx->ctx_fl_going_zombie || ctx->ctx_state == PFM_CTX_ZOMBIE) goto do_zombie;
-
+ if (ctx->ctx_fl_going_zombie || ctx->ctx_state == PFM_CTX_ZOMBIE)
+ goto do_zombie;
//if (CTX_OVFL_NOBLOCK(ctx)) goto skip_blocking;
- if (reason == PFM_TRAP_REASON_RESET) goto skip_blocking;
+ if (reason == PFM_TRAP_REASON_RESET)
+ goto skip_blocking;
/*
* restore interrupt mask to what it was on entry.
@@ -5110,7 +5113,8 @@ do_zombie:
/*
* in case of interruption of down() we don't restart anything
*/
- if (ret < 0) goto nothing_to_do;
+ if (ret < 0)
+ goto nothing_to_do;
skip_blocking:
pfm_resume_after_ovfl(ctx, ovfl_regs, regs);
diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
index 58dcfac..c7d4885 100644
--- a/arch/ia64/kernel/process.c
+++ b/arch/ia64/kernel/process.c
@@ -167,11 +167,18 @@ void tsk_clear_notify_resume(struct task_struct *tsk)
clear_ti_thread_flag(task_thread_info(tsk), TIF_NOTIFY_RESUME);
}
+/*
+ * do_notify_resume_user():
+ * Called from notify_from_user at entry.S, with interrupts disabled.
+ */
void
-do_notify_resume_user (sigset_t *unused, struct sigscratch *scr, long in_syscall)
+do_notify_resume_user(sigset_t *unused, struct sigscratch *scr, long in_syscall)
{
if (fsys_mode(current, &scr->pt)) {
- /* defer signal-handling etc. until we return to privilege-level 0. */
+ /*
+ * defer signal-handling etc. until we return to
+ * privilege-level 0.
+ */
if (!ia64_psr(&scr->pt)->lp)
ia64_psr(&scr->pt)->lp = 1;
return;
@@ -179,16 +186,26 @@ do_notify_resume_user (sigset_t *unused, struct sigscratch *scr, long in_syscall
#ifdef CONFIG_PERFMON
if (current->thread.pfm_needs_checking)
+ /*
+ * Note: pfm_handle_work() allow us to call it with interrupts
+ * disabled, and may enable interrupts within the function.
+ */
pfm_handle_work();
#endif
/* deal with pending signal delivery */
- if (test_thread_flag(TIF_SIGPENDING))
+ if (test_thread_flag(TIF_SIGPENDING)) {
+ local_irq_enable(); /* force interrupt enable */
ia64_do_signal(scr, in_syscall);
+ }
/* copy user rbs to kernel rbs */
- if (unlikely(test_thread_flag(TIF_RESTORE_RSE)))
+ if (unlikely(test_thread_flag(TIF_RESTORE_RSE))) {
+ local_irq_enable(); /* force interrupt enable */
ia64_sync_krbs();
+ }
+
+ local_irq_disable(); /* force interrupt disable */
}
static int pal_halt = 1;
--
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