If a suspend_blocker is active, suspend will fail anyway. Sincetry_to_freeze_tasks can take up to 20 seconds to complete or fail, abortingas soon as someone blocks suspend (e.g. from an interrupt handler) improvesthe worst case wakeup latency.
On an older kernel where task freezing could fail for processes attachedto a debugger, this fixed a problem where the device sometimes hung for20 seconds before the screen turned on.
Signed-off-by: Arve Hjønnevåg <arve@xxxxxxxxxxx>--- kernel/power/process.c | 23 ++++++++++++++++++----- 1 files changed, 18 insertions(+), 5 deletions(-)
diff --git a/kernel/power/process.c b/kernel/power/process.cindex ca63401..76d7cdb 100644--- a/kernel/power/process.c+++ b/kernel/power/process.c@@ -13,6 +13,7 @@ #include <linux/module.h> #include <linux/syscalls.h> #include <linux/freezer.h>+#include <linux/suspend_block.h> /* * Timeout for stopping processes@@ -36,6 +37,7 @@ static int try_to_freeze_tasks(bool sig_only) struct timeval start, end; u64 elapsed_csecs64; unsigned int elapsed_csecs;+ unsigned int wakeup = 0; do_gettimeofday(&start); @@ -62,6 +64,10 @@ static int try_to_freeze_tasks(bool sig_only) } while_each_thread(g, p); read_unlock(&tasklist_lock); yield(); /* Yield is okay here */+ if (todo && suspend_is_blocked()) {+ wakeup = 1;+ break;+ } if (time_after(jiffies, end_time)) break; } while (todo);@@ -77,11 +83,18 @@ static int try_to_freeze_tasks(bool sig_only) * and caller must call thaw_processes() if something fails), * but it cleans up leftover PF_FREEZE requests. */- printk("\n");- printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "- "(%d tasks refusing to freeze):\n",- elapsed_csecs / 100, elapsed_csecs % 100, todo);- show_state();+ if (wakeup) {+ printk("\n");+ printk(KERN_ERR "Freezing of %s aborted\n",+ sig_only ? "user space " : "tasks ");+ } else {+ printk("\n");+ printk(KERN_ERR+ "Freezing of tasks failed after %d.%02d seconds "+ "(%d tasks refusing to freeze):\n",+ elapsed_csecs / 100, elapsed_csecs % 100, todo);+ show_state();+ } read_lock(&tasklist_lock); do_each_thread(g, p) { task_lock(p);-- 1.6.1
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