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d715ff8acb
The purpose of srv_mutex is to protect srv_list as in put_srv, so no need
to hold it when allocate memory for srv since it could be time consuming.
Otherwise if one machine has limited memory, rsrv_close_work could be
blocked for a longer time due to the mutex is held by get_or_create_srv
since it can't get memory in time.
INFO: task kworker/1:1:27478 blocked for more than 120 seconds.
Tainted: G O 4.14.171-1-storage #4.14.171-1.3~deb9
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/1:1 D 0 27478 2 0x80000000
Workqueue: rtrs_server_wq rtrs_srv_close_work [rtrs_server]
Call Trace:
? __schedule+0x38c/0x7e0
schedule+0x32/0x80
schedule_preempt_disabled+0xa/0x10
__mutex_lock.isra.2+0x25e/0x4d0
? put_srv+0x44/0x100 [rtrs_server]
put_srv+0x44/0x100 [rtrs_server]
rtrs_srv_close_work+0x16c/0x280 [rtrs_server]
process_one_work+0x1c5/0x3c0
worker_thread+0x47/0x3e0
kthread+0xfc/0x130
? trace_event_raw_event_workqueue_execute_start+0xa0/0xa0
? kthread_create_on_node+0x70/0x70
ret_from_fork+0x1f/0x30
Let's move all the logics from __find_srv_and_get and __alloc_srv to
get_or_create_srv, and remove the two functions. Then it should be safe
for multiple processes to access the same srv since it is protected with
srv_mutex.
And since we don't want to allocate chunks with srv_mutex held, let's
check the srv->refcount after get srv because the chunks could not be
allocated yet.
Fixes: 9cb8374804 ("RDMA/rtrs: server: main functionality")
Link: https://lore.kernel.org/r/20201023074353.21946-6-jinpu.wang@cloud.ionos.com
Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.