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authorPeter Zijlstra <peterz@infradead.org>2020-05-26 19:11:04 +0300
committerIngo Molnar <mingo@kernel.org>2020-05-28 11:54:16 +0300
commita148866489fbe243c936fe43e4525d8dbfa0318f (patch)
tree5431e4fee20e79f58991f4c58161adf21b287ad5 /include/linux/smp.h
parent126c2092e5c8b28623cb890cd2930aa292410676 (diff)
downloadlinux-a148866489fbe243c936fe43e4525d8dbfa0318f.tar.xz
sched: Replace rq::wake_list
The recent commit: 90b5363acd47 ("sched: Clean up scheduler_ipi()") got smp_call_function_single_async() subtly wrong. Even though it will return -EBUSY when trying to re-use a csd, that condition is not atomic and still requires external serialization. The change in ttwu_queue_remote() got this wrong. While on first reading ttwu_queue_remote() has an atomic test-and-set that appears to serialize the use, the matching 'release' is not in the right place to actually guarantee this serialization. The actual race is vs the sched_ttwu_pending() call in the idle loop; that can run the wakeup-list without consuming the CSD. Instead of trying to chain the lists, merge them. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20200526161908.129371594@infradead.org
Diffstat (limited to 'include/linux/smp.h')
-rw-r--r--include/linux/smp.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/smp.h b/include/linux/smp.h
index 45ad6e30f398..84f90e24ed6f 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -25,6 +25,7 @@ enum {
CSD_TYPE_ASYNC = 0x00,
CSD_TYPE_SYNC = 0x10,
CSD_TYPE_IRQ_WORK = 0x20,
+ CSD_TYPE_TTWU = 0x30,
CSD_FLAG_TYPE_MASK = 0xF0,
};