Page faults generated walking userspace stacks can call schedule to switch out the task. When collecting callchains for scheduler tracepoints this causes a deadlock as the tracepoints can be hit with the runqueue lock held: [ 8138.159054] WARNING: CPU: 758 PID: 12488 at /opt/dahern/linux.git/arch/sparc/kernel/nmi.c:80 perfctr_irq+0x1f8/0x2b4() [ 8138.203152] Watchdog detected hard LOCKUP on cpu 758 [ 8138.410969] CPU: 758 PID: 12488 Comm: perf Not tainted 4.0.0-rc6+ #6 [ 8138.437146] Call Trace: [ 8138.447193] [000000000045cdd4] warn_slowpath_common+0x7c/0xa0 [ 8138.471238] [000000000045ce90] warn_slowpath_fmt+0x30/0x40 [ 8138.494189] [0000000000983e38] perfctr_irq+0x1f8/0x2b4 [ 8138.515716] [00000000004209f4] tl0_irq15+0x14/0x20 [ 8138.535791] [00000000009839ec] _raw_spin_trylock_bh+0x68/0x108 [ 8138.560180] [0000000000980018] __schedule+0xcc/0x710 [ 8138.580981] [00000000009806dc] preempt_schedule_common+0x10/0x3c [ 8138.606082] [000000000098077c] _cond_resched+0x34/0x44 [ 8138.627603] [0000000000565990] kmem_cache_alloc_node+0x24/0x1a0 [ 8138.652345] [0000000000450b60] tsb_grow+0xac/0x488 [ 8138.672429] [0000000000985040] do_sparc64_fault+0x4dc/0x6e4 [ 8138.695736] [0000000000407c2c] sparc64_realfault_common+0x10/0x20 [ 8138.721202] [00000000006f2e24] NG4copy_from_user+0xa4/0x3c0 [ 8138.744510] [000000000044f900] perf_callchain_user+0x5c/0x6c [ 8138.768182] [0000000000517b5c] perf_callchain+0x16c/0x19c [ 8138.790774] [0000000000515f84] perf_prepare_sample+0x68/0x218 [ 8138.814801] ---[ end trace 42ca6294b1ff7573 ]--- As with PowerPC (b59a1bfcc240, "powerpc/perf: Disable pagefaults during callchain stack read") disable pagefaults while walking userspace stacks. Signed-off-by: David Ahern <david.ahern@xxxxxxxxxx> --- arch/sparc/kernel/perf_event.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/sparc/kernel/perf_event.c b/arch/sparc/kernel/perf_event.c index 59cf917a77b5..48387be665e9 100644 --- a/arch/sparc/kernel/perf_event.c +++ b/arch/sparc/kernel/perf_event.c @@ -21,7 +21,7 @@ #include <asm/stacktrace.h> #include <asm/cpudata.h> -#include <asm/uaccess.h> +#include <linux/uaccess.h> #include <linux/atomic.h> #include <asm/nmi.h> #include <asm/pcr.h> @@ -1803,8 +1803,13 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs) return; flushw_user(); + + pagefault_disable(); + if (test_thread_flag(TIF_32BIT)) perf_callchain_user_32(entry, regs); else perf_callchain_user_64(entry, regs); + + pagefault_enable(); } -- 2.3.0 -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
