This time with LKML CC'ed. Sorry for the duplication. ---- Subject: xtime_lock vs update_process_times From: Peter Zijlstra <[EMAIL PROTECTED]>
( repost from: http://lkml.org/lkml/2008/1/28/101 ) Commit: d3d74453c34f8fd87674a8cf5b8a327c68f22e99 Subject: hrtimer: fixup the HRTIMER_CB_IRQSAFE_NO_SOFTIRQ fallback Broke several archs, since only Russel bothered to merge the fix, and Greg to ACK his arch, I'm sending this for merger. I have confirmation that the Alpha bit results in a booting kernel. That leaves: blackfin, frv, sh and sparc untested. The deadlock in question was found by Russell: IRQ handle -> timer_tick() - xtime seqlock held for write -> update_process_times() -> run_local_timers() -> hrtimer_run_queues() -> hrtimer_get_softirq_time() - tries to get a read lock Now, Thomas assures me the fix is trivial, only do_timer() needs to be done under the xtime_lock, and update_process_times() can savely be removed from under it. Signed-off-by: Peter Zijlstra <[EMAIL PROTECTED]> Acked-by: Greg Ungerer <[EMAIL PROTECTED]> CC: [EMAIL PROTECTED] CC: [EMAIL PROTECTED] CC: [EMAIL PROTECTED] CC: [EMAIL PROTECTED] CC: [EMAIL PROTECTED] --- arch/alpha/kernel/time.c | 15 ++++++++------- arch/blackfin/kernel/time.c | 8 +++++--- arch/frv/kernel/time.c | 6 ++++-- arch/m68knommu/kernel/time.c | 12 +++++++----- arch/sh/kernel/timers/timer-cmt.c | 9 --------- arch/sh/kernel/timers/timer-mtu2.c | 2 -- arch/sparc/kernel/pcic.c | 2 +- arch/sparc/kernel/time.c | 7 +++---- 8 files changed, 28 insertions(+), 33 deletions(-) Index: linux-2.6/arch/alpha/kernel/time.c =================================================================== --- linux-2.6.orig/arch/alpha/kernel/time.c +++ linux-2.6/arch/alpha/kernel/time.c @@ -119,13 +119,8 @@ irqreturn_t timer_interrupt(int irq, voi state.partial_tick = delta & ((1UL << FIX_SHIFT) - 1); nticks = delta >> FIX_SHIFT; - while (nticks > 0) { - do_timer(1); -#ifndef CONFIG_SMP - update_process_times(user_mode(get_irq_regs())); -#endif - nticks--; - } + if (nticks) + do_timer(nticks); /* * If we have an externally synchronized Linux clock, then update @@ -141,6 +136,12 @@ irqreturn_t timer_interrupt(int irq, voi } write_sequnlock(&xtime_lock); + +#ifndef CONFIG_SMP + while (nticks--) + update_process_times(user_mode(get_irq_regs())); +#endif + return IRQ_HANDLED; } Index: linux-2.6/arch/blackfin/kernel/time.c =================================================================== --- linux-2.6.orig/arch/blackfin/kernel/time.c +++ linux-2.6/arch/blackfin/kernel/time.c @@ -137,9 +137,6 @@ irqreturn_t timer_interrupt(int irq, voi do_timer(1); -#ifndef CONFIG_SMP - update_process_times(user_mode(get_irq_regs())); -#endif profile_tick(CPU_PROFILING); /* @@ -161,6 +158,11 @@ irqreturn_t timer_interrupt(int irq, voi last_rtc_update = xtime.tv_sec - 600; } write_sequnlock(&xtime_lock); + +#ifndef CONFIG_SMP + update_process_times(user_mode(get_irq_regs())); +#endif + return IRQ_HANDLED; } Index: linux-2.6/arch/frv/kernel/time.c =================================================================== --- linux-2.6.orig/arch/frv/kernel/time.c +++ linux-2.6/arch/frv/kernel/time.c @@ -63,6 +63,7 @@ static irqreturn_t timer_interrupt(int i /* last time the cmos clock got updated */ static long last_rtc_update = 0; + profile_tick(CPU_PROFILING); /* * Here we are in the timer irq handler. We just have irqs locally * disabled but we don't know if the timer_bh is running on the other @@ -73,8 +74,6 @@ static irqreturn_t timer_interrupt(int i write_seqlock(&xtime_lock); do_timer(1); - update_process_times(user_mode(get_irq_regs())); - profile_tick(CPU_PROFILING); /* * If we have an externally synchronized Linux clock, then update @@ -99,6 +98,9 @@ static irqreturn_t timer_interrupt(int i #endif /* CONFIG_HEARTBEAT */ write_sequnlock(&xtime_lock); + + update_process_times(user_mode(get_irq_regs())); + return IRQ_HANDLED; } Index: linux-2.6/arch/m68knommu/kernel/time.c =================================================================== --- linux-2.6.orig/arch/m68knommu/kernel/time.c +++ linux-2.6/arch/m68knommu/kernel/time.c @@ -42,14 +42,12 @@ irqreturn_t arch_timer_interrupt(int irq /* last time the cmos clock got updated */ static long last_rtc_update=0; + if (current->pid) + profile_tick(CPU_PROFILING); + write_seqlock(&xtime_lock); do_timer(1); -#ifndef CONFIG_SMP - update_process_times(user_mode(get_irq_regs())); -#endif - if (current->pid) - profile_tick(CPU_PROFILING); /* * If we have an externally synchronized Linux clock, then update @@ -67,6 +65,10 @@ irqreturn_t arch_timer_interrupt(int irq } write_sequnlock(&xtime_lock); + +#ifndef CONFIG_SMP + update_process_times(user_mode(get_irq_regs())); +#endif return(IRQ_HANDLED); } Index: linux-2.6/arch/sh/kernel/timers/timer-cmt.c =================================================================== --- linux-2.6.orig/arch/sh/kernel/timers/timer-cmt.c +++ linux-2.6/arch/sh/kernel/timers/timer-cmt.c @@ -100,16 +100,7 @@ static irqreturn_t cmt_timer_interrupt(i timer_status &= ~0x80; ctrl_outw(timer_status, CMT_CMCSR_0); - /* - * Here we are in the timer irq handler. We just have irqs locally - * disabled but we don't know if the timer_bh is running on the other - * CPU. We need to avoid to SMP race with it. NOTE: we don' t need - * the irq version of write_lock because as just said we have irq - * locally disabled. -arca - */ - write_seqlock(&xtime_lock); handle_timer_tick(); - write_sequnlock(&xtime_lock); return IRQ_HANDLED; } Index: linux-2.6/arch/sh/kernel/timers/timer-mtu2.c =================================================================== --- linux-2.6.orig/arch/sh/kernel/timers/timer-mtu2.c +++ linux-2.6/arch/sh/kernel/timers/timer-mtu2.c @@ -100,9 +100,7 @@ static irqreturn_t mtu2_timer_interrupt( ctrl_outb(timer_status, MTU2_TSR_1); /* Do timer tick */ - write_seqlock(&xtime_lock); handle_timer_tick(); - write_sequnlock(&xtime_lock); return IRQ_HANDLED; } Index: linux-2.6/arch/sparc/kernel/pcic.c =================================================================== --- linux-2.6.orig/arch/sparc/kernel/pcic.c +++ linux-2.6/arch/sparc/kernel/pcic.c @@ -713,10 +713,10 @@ static irqreturn_t pcic_timer_handler (i write_seqlock(&xtime_lock); /* Dummy, to show that we remember */ pcic_clear_clock_irq(); do_timer(1); + write_sequnlock(&xtime_lock); #ifndef CONFIG_SMP update_process_times(user_mode(get_irq_regs())); #endif - write_sequnlock(&xtime_lock); return IRQ_HANDLED; } Index: linux-2.6/arch/sparc/kernel/time.c =================================================================== --- linux-2.6.orig/arch/sparc/kernel/time.c +++ linux-2.6/arch/sparc/kernel/time.c @@ -128,10 +128,6 @@ irqreturn_t timer_interrupt(int irq, voi clear_clock_irq(); do_timer(1); -#ifndef CONFIG_SMP - update_process_times(user_mode(get_irq_regs())); -#endif - /* Determine when to update the Mostek clock. */ if (ntp_synced() && @@ -145,6 +141,9 @@ irqreturn_t timer_interrupt(int irq, voi } write_sequnlock(&xtime_lock); +#ifndef CONFIG_SMP + update_process_times(user_mode(get_irq_regs())); +#endif return IRQ_HANDLED; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
