git: mrsas(4): Fix lost wakeups by restoring two wait queues

[Aaron LI]

commit fdfb91da8b6b1e38f33a717e044483bcb04ebfc9
Author: Aaron LI <aly at aaronly.me>
Date:   Thu Oct 15 20:07:18 2026 +0800

    mrsas(4): Fix lost wakeups by restoring two wait queues
    
    mrsas(4) is a port of the Linux megaraid_sas driver (see e.g. v3.13).
    The port translated Linux's wake_up(), which wakes every non-exclusive
    waiters on a wait queue, as wakeup_one(), which wakes only one. It also
    collapsed Linux driver's two wait queues ('int_cmd_wait_q' for internal
    DCMDs and 'abort_cmd_wait_q' for aborts) into the single 'sc->chan'
    channel.
    
    Both loops wait on a per-command predicate (cmd->cmd_status), so a
    single wakeup on a shared channel can wake the wrong thread and drop the
    wakeup for the command that actually completed.  With two blocked
    commands outstanding, one of them then times out after
    MRSAS_INTERNAL_CMD_WAIT_TIME even though it completed.
    
    Fix the problem by correct the two porting issues:
    
    * internal DCMDs continue to use 'sc->int_chan' that is renamed from
      'sc->chan', woken by mrsas_wakeup();
    * aborts use a new 'sc->abort_chan', woken by mrsas_complete_abort();
    * both use wakeup(), matching the original Linux's wake_up() semantics.
    
    In addition, remove the meaniningless 'sc->chan = (void *)&cmd'
    assignments.  This also fixes the following '-Wdangling-pointer'
    warnings from GCC 12.5.  Also change the channel type from 'void *' to
    'u_int8_t' since only its address in the struct matters, so this makes
    the dangling-pointer class of bug structurally impossible.
    
    ```
    /usr/src/sys/dev/raid/mrsas/mrsas.c: In function 'mrsas_issue_blocked_cmd':
    /usr/src/sys/dev/raid/mrsas/mrsas.c:2880:14: warning: storing the address of local variable 'cmd' in '*sc.chan' [-Wdangling-pointer=]
     2880 |     sc->chan = (void*)&cmd;
          |     ~~~~~~~~~^~~~~~~~~~~~~
    /usr/src/sys/dev/raid/mrsas/mrsas.c:2865:75: note: 'cmd' declared here
     2865 | int mrsas_issue_blocked_cmd(struct mrsas_softc *sc, struct mrsas_mfi_cmd *cmd)
          |                                                     ~~~~~~~~~~~~~~~~~~~~~~^~~
    /usr/src/sys/dev/raid/mrsas/mrsas.c:2865:75: note: 'sc' declared here
    ```
    
    Assisted-by: DeepSeek-v4.1-flash (with Pi Coding Agent)

Summary of changes:
 sys/dev/raid/mrsas/mrsas.c | 20 ++++----------------
 sys/dev/raid/mrsas/mrsas.h |  5 +++--
 2 files changed, 7 insertions(+), 18 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/fdfb91da8b6b1e38f33a717e044483bcb04ebfc9


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