3.2.102-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: "K.Prasad" <[email protected]> commit 500ad2d8b01390c98bc6dce068bccfa9534b8212 upstream. While debugging a warning message on PowerPC while using hardware breakpoints, it was discovered that when perf_event_disable is invoked through hw_breakpoint_handler function with interrupts disabled, a subsequent IPI in the code path would trigger a WARN_ON_ONCE message in smp_call_function_single function. This patch calls __perf_event_disable() when interrupts are already disabled, instead of perf_event_disable(). Reported-by: Edjunior Barbosa Machado <[email protected]> Signed-off-by: K.Prasad <[email protected]> [[email protected]: v3: Check to make sure we target current task] Signed-off-by: Naveen N. Rao <[email protected]> Acked-by: Frederic Weisbecker <[email protected]> Signed-off-by: Peter Zijlstra <[email protected]> Link: http://lkml.kernel.org/r/[email protected] [ Fixed build error on MIPS. ] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Ben Hutchings <[email protected]> --- include/linux/perf_event.h | 2 ++ kernel/events/core.c | 2 +- kernel/events/hw_breakpoint.c | 11 ++++++++++- 3 files changed, 13 insertions(+), 2 deletions(-) --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1140,6 +1140,7 @@ extern int perf_swevent_get_recursion_co extern void perf_swevent_put_recursion_context(int rctx); extern void perf_event_enable(struct perf_event *event); extern void perf_event_disable(struct perf_event *event); +extern int __perf_event_disable(void *info); extern void perf_event_task_tick(void); #else static inline void @@ -1178,6 +1179,7 @@ static inline int perf_swevent_get_recu static inline void perf_swevent_put_recursion_context(int rctx) { } static inline void perf_event_enable(struct perf_event *event) { } static inline void perf_event_disable(struct perf_event *event) { } +static inline int __perf_event_disable(void *info) { return -1; } static inline void perf_event_task_tick(void) { } #endif --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1344,7 +1344,7 @@ retry: /* * Cross CPU call to disable a performance event */ -static int __perf_event_disable(void *info) +int __perf_event_disable(void *info) { struct perf_event *event = info; struct perf_event_context *ctx = event->ctx; --- a/kernel/events/hw_breakpoint.c +++ b/kernel/events/hw_breakpoint.c @@ -453,7 +453,16 @@ int modify_user_hw_breakpoint(struct per int old_type = bp->attr.bp_type; int err = 0; - perf_event_disable(bp); + /* + * modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it + * will not be possible to raise IPIs that invoke __perf_event_disable. + * So call the function directly after making sure we are targeting the + * current task. + */ + if (irqs_disabled() && bp->ctx && bp->ctx->task == current) + __perf_event_disable(bp); + else + perf_event_disable(bp); bp->attr.bp_addr = attr->bp_addr; bp->attr.bp_type = attr->bp_type;
